The San Francisco 49ers were in trouble on Sunday when they lost Jimmy Garoppolo to a foot injury early against the Miami Dolphins.

But backup quarterback Brock Purdy played well in his absence, and Tua Tagovailoa had his worst game of the season in a 33-17 49ers win.

Jimmy Garoppolo is done for season

The win was overshadowed postgame by the news that Garoppolo is done for the year with broken bones in his injured left foot. Head coach Kyle Shanahan announced the news to reporters in his news conference.

"Jimmy's a hell of a player," Shanahan told reporters after the game. "Like I said last week, we were so fortunate to have him here. But we need everybody.

"Today we needed a good defense. We needed a good run game. We needed guys to step it up at wideout and tight end. And we needed our quarterback to come in and do his job. All those guys did that at a pretty high level today."

Garoppolo, the longtime starter in San Francisco, began the season as the 49ers' backup to 2021 first-round pick Trey Lance. He took over when Lance sustained a season-ending injury in Week 2, and now the 49ers will presumably look to their third-string quarterback Purdy moving forward. ESPN's Adam Schefter reports that the 49ers are signing veteran journeyman Josh Johnson off the Denver Broncos practice squad to bolster the quarterback depth chart.

Tua struggles against strong 49ers defense

While the 49ers regrouped following Garoppolo's injury, Tagovailoa struggled for most of the game. The Dolphins scored 14 points on a pair of big plays that accounted for 120 of his passing yards. Besides those plays, the efficiency that that's become Tagovailoa's trademark was largely missing.

Some of it's a credit to a swarming 49ers defense that leads the league in points and yards allowed. Nick Bosa sacked Tagovailoa three times and hit him three others. But several of Tagovailoa's miscues were unforced. He missed multiple passes in the first half that weren't under duress. Then in the second half, he turned the ball over on consecutive possessions.

With 10:10 left in the third and the 49ers leading 17-10, Tagovailoa faced a collapsing pocket on first-and-25. With a pair of 49ers pass rushers charging, Tagovailoa stepped up and fired a pass in traffic to Jeff Wilson Jr. Wilson, who slipped and watched as 49ers linebacker Jimmie Ward pounced on the ball for an interception.

The turnover broke a streak of 193 Tagovailoa passes without an interception, a Dolphins record. On his very next pass, Tagovailoa turned the ball over again.

This time, he targeted Tyreek Hill in the flat after rolling out to his left. The pass was high and behind Hill and bounced off his hands and into those of 49ers cornerback Deommodore Lenoir. The turnover set up a 49ers field goal to extend their lead to 23-10.

Tagovailoa's third turnover arrived on a strip-sack by Bosa that Dre Greenlaw returned for a touchdown to extend San Francisco's lead to 33-17 and ice the game.

Tagovailoa finished the game completing 18 of 33 passes for 295 yards with two touchdowns and two interceptions. His 54.5% completion rate fell well below his season mark of 67.3%. Meanwhile, the 49ers got enough out of Purdy, who kept the offense moving in Garoppolo's stead and limited himself to a single turnover.

The win is a testament to a surging 49ers team that's now won five straight to improve to 8-4 and maintain its lead over the 7-5 Seattle Seahawks in the NFC West. Its defense flustered an outstanding Dolphins offense while the offense designed to get the ball into the hands of its playmakers continued to execute with its starting quarterback sidelined.

Christian McCaffrey has one of his best games since joining San Francisco while tallying 66 rushing yards alongside 80 yards and a touchdown on eight catches. His 30-yard run late in the fourth quarter set up a Robbie Gould field goal that extended San Francisco's lead to two possessions.

Meanwhile, Deebo Samuel tallied 63 yards from scrimmage while Brandon Aiyuk totaled four catches for 56 yards. Purdy finished the day completing 25 of 37 passes for two touchdowns and an interception. It wasn't vintage 49ers offense. But it was a sign that the unit can continue to function in Garoppolo's absence.

For the Dolphins, the loss drops them to 8-4 and a game behind the Buffalo Bills in the AFC East. It also pumps the brakes on a breakout season for Tagovailoa and the Miami offense.