Game Preview: Athletics At Astros

(AP) - The upstart Houston Astros have not allowed youth to prevent them from racing towards the top of the AL.

Looking to extend yet another winning streak, the Astros will get even younger Monday night when they turn to Lance McCullers, who will face the sputtering Oakland Athletics in his major league debut.

Houston (25-13) became the first team to 25 wins and pushed its winning streak to five with a 4-2 victory over Toronto on Sunday. Collin McHugh pitched seven strong innings for the Astros, who have enjoyed three winning streaks of four or more games despite rostering no active position players older than 29.

Elder statesmen Luis Valbuena (29) and Colby Rasmus (28) hit home runs Sunday to cap Houston's four-game sweep.

"It's a great tribute to the players and leadership we have," manager A.J. Hinch told MLB's official website. "Sometimes you're ahead, sometimes you're behind, but you're never out of it. That's the way we're going about it."

Their youngest active player is now McCullers, whose call-up came in a somewhat surprising move.

The 21-year-old right-hander dropped from Houston's fifth-best prospect in 2014 to No. 10, according to MLB.com, following a 5.47 ERA in 97 innings last season at High-A. But he began 2015 at Double-A Corpus Christie where he dazzled with a 0.62 ERA in six appearances, allowing only 15 hits and two earned runs while striking out 43 through 29 innings.

McCullers was promoted to Triple-A on Thursday, but had yet to make an appearance. He fills the rotation spot vacated by Brett Oberholtzer, who suffered a blister on his pitching hand.

"We believe he's got the repertoire and stuff to pitch in the big leagues and be successful," Astros general manager Jeff Luhnow said. "There are other pitchers we have in Triple-A and Double-A that are close, but when we looked at ouroptions, he gives us the best chance to win on Monday."

McCullers will face an Oakland team that has lost 10 of 11 and is last in the AL West, 12 1/2 games behind the division-leading Astros.

Exactly one year ago, last-place Houston trailed the first-place Athletics by 12 games.

The A's (13-26) fell to the Chicago White Sox 7-3 on Sunday for a fourth straight defeat and now head back on the road where they've lost five straight.

Drew Pomeranz (2-3, 4.42 ERA) is 0-3 with a 6.86 ERA in four road starts this season, which includes allowing four runs in five-plus innings of a 6-1 loss at Houston on April 15. At home against the Astros 11 days later, the left-hander gave up five runs - three earned - in five innings of a 7-6 defeat.

Jose Altuve is 4 for 6 against Pomeranz this year, batting .444 (12 for 27) in the season series and has hit safely in 29 straight games against Oakland. The White Sox's Luke Appling has baseball's longest hitting streak against the Athletics, hitting safely in 31 straight from 1939-1940.

Pomeranz allowed one earned run and three hits over seven innings of Tuesday's 9-2 victory over Boston - the Athletics' only win since May 6.

"Sometimes his confidence goes the other way and he starts taking a little more time, it kind of snowballs on him," manager Bob Melvin said. "But (Tuesday) ... as the game went along you could see the confidence grow and grow."

Updated May 17, 2015