“I can’t even begin to compare what he’s demonstrating,” Manager John Farrell said of Xander Bogaerts, above. (Paul Sancya/Associated Press)

At the beginning of the season, the Boston Red Sox weren’t supposed to be here, and if they were, Xander Bogaerts certainly wasn’t penciled into the starting lineup. But for the second straight game in the American League Championship Series , there was the 21-year-old rookie at third base — nervous on the inside, not the outside.

“I can’t even begin to compare what he’s demonstrating,” Manager John Farrell said. “I would hope he would be nervous inside. That would only be, I think, a natural response. But at the same time he’s able to control it, and it doesn’t take him out of his approach or how he plays the game.”

Since becoming a pro at 17, the native of the Caribbean island of Aruba entered the season as Boston’s top prospect as ranked by the trade magazine Baseball America. Other than 10 games at third base this season for Class AAA Pawtucket, Bogaerts played shortstop as he came up through the minors. He began this season at Class AA Portland, and was promoted after he hit .311 with a .909 on-base-plus-slugging percentage. He played 60 games at Pawtucket, hitting .284, before making his major league debut Aug. 20.

“Wow, it’s a crazy year, I would say,” Bogaerts said. “Very blessed. I mean, sometimes I can’t even believe I’m here. At 21 and starting in Double-A, and now here in the ALCS, one game away from the World Series, sometimes it’s hard to believe.”

Stephen Drew has served as Boston’s regular shortstop since the team dealt Jose Iglesias to Detroit in July. But Drew is here on a one-year, $9.5 million deal, so that position should be Bogaerts’s going forward.

For now, though, Bogaerts is pleased to fit in wherever he can. In six postseason games, he has three hits — all doubles — in six at-bats, five walks and seven runs scored.

“It’s been really fun to see, actually,” Farrell said. “The smile on his face never goes away. There’s never the look on his face, there’s no deer in the headlights, any kind of those descriptions you might come up with. He’s a very mature and poised young man.”

Avila stays in the lineup

Tigers catcher Alex Avila was in the lineup for Game 6 two days after injuring his left knee in a home-plate collision with Red Sox catcher David Ross. Avila was lifted in the fourth inning of Game 5 for a pinch hitter, but Detroit Manager Jim Leyland said before Saturday’s game that he expected Avila would be able to play nine innings, which he did.

“The one thing you don’t want to happen is start the game and take him out in the second or third inning,” Leyland said. “That’s one thing I try to guard against as a manager. If you can’t go, that’s fine. But if you can go, you want to be out for the entire game, if possible.”

Avila hit a two-run homer off Boston’s Game 6 starter, Clay Buchholz, in Game 2. . . .

Following Saturday’s win, the Red Sox are now 6-0 in Game 6s of the ALCS. They had never before held a 3-2 lead after five games of an ALCS.