He's only been a big leaguer for five months, but this much seems clear: Tonight is the biggest start of Adalberto Mejia's career thus far.

And he knows it.

"It's an important day for me. I feel a responsibility and a duty to go out there and win," Mejia said of his start tonight against the Blue Jays. "All my games in the big leagues, I've taken seriously. But there's a lot of seriousness about this one."

There are personal factors and team factors that make that true. The 24-year-old lefthander is returning from a biceps injury that has kept him out of action since Aug. 8. The Twins have auditioned seemingly every pitcher in Triple-A for their fifth rotation spot this season, but Mejia would like to nail that job down, for the rest of this season and the future.

"I think I'm the same pitcher as before the injury," said Mejia, who enters the game with a 4.47 ERA in 18 starts as an MLB rookie. "The rehab time gave me a little awareness about how to be a better pitcher, so I think I've learned from it."

And then there's the pennant race. The Twins own the second AL wild card spot, but their lead was reduced to two games with last night's loss, and they have six games coming up in New York and Cleveland, which will be a challenge. The Twins need to keep winning, and Mejia knows it.

"The team is in a fight for the playoffs, and I want to help us get there, obviously," Mejia said. "This game might mean everything to us at the end. You don't know, so you just have to go out and win."

Twins manager Paul Molitor said he has no doubt that giving Mejia the start over Aaron Slegers is the right call, citing Mejia's experience gained during the season. Mejia is a rookie, in other words, but it doesn't feel like it.

"It's like freshman basketball players playing in March Madness. Hopefully by the time you get near the end, you're feeling pretty comfortable," Molitor said. "There's a little more risk with his limited experience, but I'm not overly concerned it's going to have a big effect on him."

Still, Molitor said he might limit Mejia's pitch count to 80 or 90, with Slegers available in the bullpen.

Here are the lineups for tonight's game at overcast Target Field:

BLUE JAYS

Hernandez LF

Donaldson 3B

Smoak 1B

Bautista RF

Morales DH

Pillar CF

Martin C

Barney 2B

Urena SS

Estrada RHP

TWINS

Dozier 2B

Mauer 1B

Polanco SS

Rosario LF

Buxton CF

Kepler RF

Escobar 3B

Castro C

Grossman DH

Mejia LHP