(SportsNetwork.com) - Right-hander Lance McCullers will make the jump from Double-A to the major leagues on Monday night when the Houston Astros begin a three-game series with the Oakland Athletics.

The 21-year-old McCullers has been dominate with Corpus Christi this season to earn his big league debut, going 3-1 with a 0.62 earned run average over six games with four starts. In that span, he allowed two earned runs and 15 hits over 29 innings while racking up 43 strikeouts.

McCullers was in line to head to Triple-A, but instead was summoned to Houston as Brett Oberholtzer returned to the disabled list because of a blister on his throwing hand.

"I don't think you ever expect your big league callup, especially when you were in Double-A, and then Triple-A for just a couple of days," McCullers told the Astros' official website. "That just shows how much confidence that the Astros have in me, and the steps I have made toward being here. I'm just happy I can help this team win."

The Astros have done a lot of winning this season, improving to 25-13 on the season thanks to a current five-game win streak. That matches the 1998 team for the best 38-game start in franchise history.

Houston finished off a four-game sweep of the Toronto Blue Jays with Sunday's 4-2 win as Colby Rasmus and Luis Valbuena both hit solo homers.

Collin McHugh followed up his first loss of the season with seven quality innings. He struck out nine and scattered six hits and two runs for AL West- leading Houston.

Oakland is at the bottom of the AL West, having lost four straight and 10 of its past 11 contests. The Athletics failed to win a game in their three-game series with the Chicago White Sox, losing Sunday's finale 7-3.

Scott Kazmir struck out six, but surrendered five runs -- three earned -- on seven hits and three walks over 4 1/3 frames for the A's, who were charged with four errors on Sunday and have posted at least one error in 14 consecutive games.

"We have to play cleaner games," A's manager Bob Melvin said.

Max Muncy launched his first career homer, a two-run shot, in defeat. He got the start after first baseman Ike Davis hit the disabled list due to a strained left quadriceps.

Drew Pomeranz takes the mound for the Athletics tonight looking to secure a second straight victory for the first time this season.

Staked to an early lead, Pomeranz held the Boston Red Sox to a pair of runs -- one earned -- on three hits over seven innings of a 9-2 victory on Tuesday. He struck out three and did not walk a batter to pick up his first win since April 10.

"He threw strikes," Melvin said of Pomeranz. "We needed him to go seven innings tonight. It's usually a good recipe when your starter goes deep into games and you play good defense."

The left-hander is 2-3 with a 4.42 ERA on the season and will be facing the Astros for the third time in 2015. He has gone 0-1 over the previous two meetings, giving up seven earned runs over 10 innings, and is 0-2 with a 6.05 ERA in five lifetime encounters, including four starts.

Houston has won four straight over the Athletics, including a three-game sweep in Oakland from April 24-26.