On Monday afternoon, Diamondbacks manager Torey Lovullo talked about how he tries not to dwell on games his team probably should have won. He calls it the “woulda coulda shoulda” game, and he reminds himself not to play it by remembering the wins the Diamondbacks stole that they had no business taking.

Lovullo will be remembering what happened later that night for a long time. So will everyone else.

The Diamondbacks trailed by five runs after one inning, by six runs after two, by four entering the bottom of the ninth. They wound up stealing a win, all right, one of the more improbable victories in franchise history.

Corbin Carroll launched a pinch-hit, ninth-inning homer for the first walk-off blast of his career, a two-run shot that completed a five-run Diamondbacks’ rally in a 9-8 win over the Washington Nationals.

They won a game in which their starter, Jordan Montgomery, gave up five runs in the first inning. They won a game by coming back on Nationals All-Star closer Kyle Finnegan, who had been considered one of the better relievers available ahead of Tuesday’s trade deadline.

And they won a game that might also be remembered for something else, something not nearly so rosy.

Diamondbacks first baseman Christian Walker exited the game after three innings with what the team is calling left oblique tightness. He is scheduled to undergo an MRI exam on Tuesday morning.

The early indications are ominous. Lovullo, who tends to err strongly on the side of optimism, acknowledged his concern over the severity of the injury. And for Walker to exit early in the first place — he has played in each of the Diamondbacks’ first 107 games this year — is alarming in its own right.

Lovullo had already begun to assume responsibility for the injury.

“I blame myself in a lot of different ways for this because I ask him to go out there every single day,” Lovullo said. “He’s only had, probably, I don’t even know, 18, 24 innings off this year. That’s on me. I have to be a little bit better managing him and I will once he gets out of this little situation. Hopefully, we get real good results tomorrow morning.”

Lovullo believed that Walker, who declined comment, might have suffered the injury during his only at-bat of the night, a strikeout in the second inning.

For as tough as Sunday afternoon’s loss was for the Diamondbacks – they led, 2-1, entering the ninth but lost, 6-5, in 10 innings to the Pittsburgh Pirates — Monday’s win was just as delightful.

They trailed, 8-4, when Alek Thomas led off the ninth by ripping a triple into the right-center field gap. Geraldo Perdomo followed with a single, and Ketel Marte quickly made it a one-run game by obliterating a Finnegan fastball, lining a homer 110.2 mph into the right field seats.

It got better from there. With one out, Lourdes Gurriel Jr. fought through a nine-pitch at-bat to shoot a single through the middle. That set the stage for Carroll.

Earlier in the day, Lovullo was asked about Carroll’s absence from his lineup and whether Lovullo was looking to give him a day off. Nobody, Lovullo said, needed a rest. The implication was obvious: Lovullo believed his best lineup for that night did not include Carroll, a conclusion he has been reaching often when opposing teams are starting lefties — and one that would have been unfathomable when the season began.

As it turned out, Lovullo couldn't have planned it any better.

The spot that was due up was occupied by Kevin Newman, the light-hitting infielder who had replaced Walker to start the fourth. Instead, Lovullo sent Carroll to the plate.

He saw a total of two pitches, both splitters, and hit both hard. The first he pulled foul down the right-field line. The next he put into the first row in right, hitting it 109.5 mph.

Carroll, who won the National League Rookie of the Year last year and finished fifth in MVP voting, has been unable to get going at the plate through the first four months of the season. Lovullo is hoping the swing Carroll put on Finnegan's hanging splitter will do the trick.

“For him to run around the bases — and I got a chance to watch him smile while he was doing it — it was pretty awesome,” Lovullo said. “I want him to go out and have the best two months of his life. He’s very capable of doing that. This could be a good catalyst to push him in that direction.”

Said Carroll: “(Hitting coach) Joe Mather said it at the beginning of last series — that we’re just never out of games. It’s truly how it’s felt. Just not over until it’s over, and we’ve been putting together some really great, late-game at-bats. It just seems like it’s been able to pay off a little bit.”

The six-run comeback was the Diamondbacks' largest in a win this season. It was just the third time in franchise history they came back from down four in the ninth inning or later. They are a major league-best 17-8 since June 29.

"That’s the type of team we are," Marte said. "We don’t give up. You’ve got to record all of those 27 outs."

—Nick Piecoro

Diamondbacks still eyeing bullpen help ahead of trade deadline

Even after adding left-hander A.J. Puk in a trade last week, the Diamondbacks remain focused on adding to their bullpen ahead of Tuesday’s 3 p.m. trade deadline, sources say.

Puk has thrown well in both of his appearances with his new club, most recently striking out the side in a scoreless inning on Sunday.

The Diamondbacks have now turned their focus to more right-handed help, eyeing another reliever they would trust to protect a lead in the middle or late innings.

The fact that they still are looking to add could signal a willingness to move on from right-hander Miguel Castro, who is still owed the remainder of his $5 million salary for this year.

Castro has spent most of the season on the injured list with shoulder trouble but has logged just a 5.40 ERA in 11 2/3 innings when he has pitched.

-Nick Piecoro

Yilber Diaz optioned; Eduardo Rodriguez could return next week

The Diamondbacks optioned right-hander Yilber Diaz to Triple-A Reno on Monday and recalled right-hander Slade Cecconi, who will provide a fresh arm in relief.

That opens a spot in the rotation that might not come up again until Tuesday in Cleveland, and manager Torey Lovullo said that left-hander Eduardo Rodriguez could be an option to step into that spot to make his season debut.

Rodriguez and right-hander Merrill Kelly are each scheduled to pitch simulated games Wednesday at Salt River Fields. Rodriguez will throw four innings and up to 60 pitches; Kelly will be at three innings and 50 pitches.

With an off day on Thursday, Lovullo said the club was leaning toward keep the other four starters on regular rest, meaning a fifth starter would not be needed until the second day of their series with the Guardians.

Assuming all goes well with Rodriguez on Wednesday, he would line up to fill that vacancy and pitch on an extra day of rest. Presumably, he would be in position to throw somewhere in the neighborhood of 75-80 pitches.

Rodriguez, whom the Diamondbacks signed to a four-year, $80 million contract in December, has not pitched yet this season due to an arm injury. He posted a 3.30 ERA in 26 starts last season with the Detroit Tigers and owns a career 4.03 ERA in parts of eight seasons in the majors.

Kelly made four starts this season before running into shoulder problems of his own. Lovullo said Kelly could also be an option for that outing in Cleveland but seemed to intimate that Rodriguez would be the more logical choice since he will be one inning and another 10 pitches ahead of him in his build up.

Diaz threw well in three of his four starts, posting a 4.05 ERA in 20 innings, but Lovullo said the club needed relief coverage. He said the team probably wouldn’t have made a move if Sunday’s game hadn’t gone to extra innings.

-Nick Piecoro

Slade Cecconi touches 99 mph in new relief role

Right-hander Slade Cecconi has been working with increased velocity since shifting to the bullpen following his demotion to Triple-A Reno earlier this month.

In five innings, Cecconi allowed just two runs with one walk and seven strikeouts – and touched 99 mph with his fastball.

Cecconi averaged 94.1 mph with his fastball and topped out at 98.5 mph during his time in the majors this year. He said his livelier fastball – he averaged 96.1 mph in relief and topped at 99.1 mph – was a topic of conversation at Chase Field upon his arrival on Monday.

“I guess word travels when you throw hard,” he said. “The first time I hit it, it was rounded up so I felt kind of guilty about it, about saying it. My last game in Reno, I told the guys in Reno I need to hit a true one so I don’t feel guilty if people ask. So I got a true one. It feels good. It’s the hardest I’ve thrown. We’ll see if I can bring it up here.”

-Nick Piecoro

Torey Lovullo sticking with Paul Sewald as closer

Manager Torey Lovullo said he is not ready to move off Paul Sewald as his closer even after Sewald blew his fourth save in nine attempts this month on Sunday against the Pittsburgh Pirates.

Lovullo noted that Sewald has converted 16 of his 20 save opportunities so far this season, and while he acknowledged it is more challenging given that the blown chances have been clustered into this month, he said he still wasn’t ready to pull the plug.

“I have to balance the (temptation) to be impatient,” Lovullo said. “Everybody’s instincts are to make a big change. That’s what everybody wants to do, except for the 26 guys in that room, me, the coaches. We are on course. I haven’t got there. If I do, I promise I will let you know. Paul will know first. But I’m not there yet. Sixteen of 20? I’ll sign up for that.”

If the Diamondbacks were to make a change, they have a number of options to consider, including setup men Ryan Thompson and Kevin Ginkel as well as Puk.

-Nick Piecoro

Tuesday’s Diamondbacks-Nationals pitching matchup

Nationals at Diamondbacks, 6:40 p.m., Cox, Ch. 34

Diamondbacks RHP Ryne Nelson (7-6, 4.85)  vs. Nationals LHP Patrick Corbin (2-10, 5.26).

At Chase Field: Nelson gave up four runs in six innings against the Royals last week and was taken off the hook for a loss when the Diamondbacks rallied for five runs in the top of the ninth inning in a game they would win, 8-6. … In five July starts, Nelson has a 2.97 ERA with six walks and 24 strikeouts in 30 1/3 innings. … Nelson has used his fastball 62.4 percent of the time this month, a higher rate than any previous month. Opponents are hitting just .190 off the pitch with a .328 slugging. … Corbin, who broke into the big leagues with the Diamondbacks, is in the final year of the six-year deal he signed with the Nationals after the 2018 season. … He continues to take the ball for the Nationals and provide innings for them, but he is going on Year 4 of being one of the worst starters in the league from a results perspective. He leads the league in earned runs allowed this year and has led in two of the previous three seasons, as well. … He has faced the Diamondbacks five times, posting an 8.87 ERA in 23 1/3 innings. 2B Ketel Marte is 5 for 12 (.417) with a double and two homers off Corbin.

Coming up

Wednesday: At Chase Field, 12:40 p.m., Diamondbacks RHP Zac Gallen (8-5, 3.70)  vs. Nationals LHP MacKenzie Gore (6-8, 4.51).

Thursday: Off.

Friday: At Pittsburgh, 3:40 p.m., Diamondbacks RHP Brandon Pfaadt (5-6, 3.92)  vs. Pirates RHP Luis Ortiz (5-2, 2.75).

Saturday: At Pittsburgh, 3:40 p.m., Diamondbacks TBA vs. Pirates LHP Marco Gonzales (1-1, 3.72).

This article originally appeared on Arizona Republic: Carroll's walk-off HR caps rally, but DBacks lose Walker to injury