The San Francisco 49ers were desperate for a big play in the second half of Sunday's NFC championship game.

They got one, with a big assist from Kindle Vildor's facemask that sparked their rally from a 17-point halftime deficit to a 34-31 win and a berth in the Super Bowl.

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With San Francisco trailing the Detroit Lions 24-10 in the third quarter, Brock Purdy looked deep to Brandon Aiyuk on first-and-10 from the 49ers' 45-yard line. He missed his target with an overthrow that Vildor had a chance to intercept. Instead, the ball bounced off Vildor's hands and then his facemask and into the hands of a diving Aiyuk at the 4-yard line.

Replay showed that Aiyuk indeed made the catch after the ball ricocheted off Vildor's helmet.

Vildor touched him down before Aiyuk hit the turf. It wasn't a touchdown, but it was a 51-yard completion. Three plays later, Purdy found Aiyuk in the end zone to cut Detroit's lead to 24-17.

It was a huge score for the 49ers, who were outplayed in the first half, which Detroit led 24-7, and for Aiyuk, who's facing offseason contract negotiations. It was also the kind of play that shifted the momentum of a game with a trip to the Super Bowl at stake.

San Francisco forced a fumble on Detroit's next possession and converted the turnover into a Christian McCaffrey touchdown run. Just like that, a 17-point Lions lead was erased. They followed it up with a field goal an Eli Mitchell touchdown, and the 49ers never trailed again.

Aiyuk: Pregame ladybug sent him good luck

After the game, Aiyuk credited a ladybug — which is a sign of good luck — with sparking his good fortune Sunday.

"Before the game, a ladybug landed on my shoe," Aiyuk told Fox's Erin Andrews. "And y'all know what that means. ... Just great luck. God was with us today. Great win. Bang bang Niner gang. It's crazy."

Ladybug or not, Aiyuk deserves credit for keeping his concentration to secure an all-time catch. The 49ers probably wouldn't be playing in the Super Bowl without it. As it is, they have their second Super Bowl date with the Kansas City Chiefs in five seasons.