With the season on the line, and regular catchers Jarrod Saltalamacchia and Jason Varitek banged up, Lavarnway stepped right into the spotlight and belted two home runs, lifting the Red Sox to an 8-7 victory over the Orioles.
Without Lavarnway's heroics, the Sox could have been staring at a one-game deficit to the Rays in the American League Wild Card standings heading into Wednesday's regular-season finale.
Instead, the clubs remain tied.
Manager Terry Francona could have forced the issue with Saltalamacchia, who injured his right collarbone on Monday. Instead, he felt Lavarnway was the best choice for this game, particularly with a lefty going for the Orioles in Zach Britton.
The move could not have worked out any better.
"He played his [butt] off," said Francona. "That was exciting. I thought, besides what he did offensively, I thought he ran the game. I thought he had a lot of poise. That was one of the more exciting things to watch. We've seen a lot of interesting things here over the years. That was right near the top."
Lavarnway's performance included the first two homers of his career on the night he started at catcher for the first time in the Majors.
"Like I said, 3-1, I caught myself cheating a little bit, so, 3-2, I stayed within myself with a middle-of-the-field approach," Lavarnway said of his three-run shot that gave Boston a 5-1 lead.
Lavarnway also contributed with his arm, throwing out Adam Jones on an attempted steal of third in the second.
"I don't even remember it," Lavarnway said. "I was just reacting. I saw Jed tag him. I said, 'Oh, I must have made a good throw.'"
Lavarnway made another big throw in the ninth, pouncing on a tapper by Matt Wieters and firing to first, just in time.
Lavarnway had started seven games for the Sox previously, but all were at designated hitter.
This time, he was thrown into the fire -- and he responded.
"It definitely feels good," Lavarnway said. "It feels like I could wear the jersey with pride, especially a little bit more now that I've helped out and am contributing. That's what I wanted to do when I got here. I didn't want to just have a September callup that was meaningless. I'm glad I could help today."
Saltalamacchia has a sore right collarbone sustained when he was dinged by a foul tip. Varitek was hit on the right knee by a pitch in Sunday night's game against the Yankees and tried to start Monday, but he was too sore.
"He came out early today," manager Terry Francona said of Saltalamacchia. "He went out and threw. He actually threw the ball OK. He's going to go hit [in the cage]."
Perhaps Saltalamacchia will start Wednesday.
"Every game I want to play, especially when we're getting down to the wire," said Saltalamacchia. "We've got two games left. I definitely want to be in there, but at the same time, I want to make sure I'm 100 percent. I don't want to go out there and hurt the team. I need to be 100 percent. I need to be able to perform. I feel good. ... I feel like I can perform, but if it takes today to be 100 percent for tomorrow, then that's what we'll do."