A big test for evolving Matt Harrison

DETROIT -- Matt Harrison will pitch in the biggest game of his life this afternoon.

Game 4 of the American League Championship Series can either push the Texas Rangers to a commanding 3-1 lead or the Detroit Tigers can gain the tie and the momentum knowing they have Justin Verlander ready to go in Game 5 back at Comerica Park.

A year ago, Harrison (1-0, 4.76) didn't make any of the Rangers' three postseason rosters. Now his team's fate very well could ride on his left arm. He hasn't pitched since going five innings in the Game 4 ALDS clincher one week ago. Harrison called it a day he will never forget.

He pitched well, allowing two runs on five hits while striking out nine.

This day is bigger.

Harrison faces Tigers starter Rick Porcello, who looked good in two innings of relief in Game 1, and a Tigers lineup that finally banged out hits with runners in scoring position and drove three balls out of the park.

"I think you just have to be aggressive against these guys," Harrison said. "Try to limit the mistakes, keep the ball in the corners. Biggest thing is being aggressive and not walking guys and putting them on base and giving them more opportunities."

Harrison's success this season can be traced to excellent command of his offspeed pitches. In his last six starts, opponents are hitting .116 (5-for-43) with 16 strikeouts. In three of those starts (all wins), Harrison did not allow a hit against his offspeed stuff, according to ESPN Stats and Info.

The 26-year-old knows his improved curveball has been a key to success. Interestingly, he said it's been easier to pinpoint his pitches than a reason why he's mastered the pitch over the course of the season.

"Honestly, I'm not really sure. I started throwing it more in games and getting a better feel for it," Harrison said. "I think the biggest thing was staying on top of it. I've been throwing more sinkers this year, and I had to stay on top of that to make sure I have more downhill plane, so I think that's helped out with my curveball to stay on top of it."

The Rangers know if Harrison can stay on top of it today, they could be in position to win the American League pennant in Game 5 on the Tigers' turf.