HOUSTON - Following the hullabaloo that accompanied his promotion on April 16, Astros rookie right fielder George Springer has endured the struggles that often greet prospects facing great expectations.

On Friday night Springer caught a break, bouncing a bases-loaded single off the glove of Mariners third baseman Kyle Seager to drive in the winning run in the bottom of the 11th inning in the Astros' 5-4 victory over the Seattle Mariners at Minute Maid Park.

Springer, 0-for-5 with four strikeouts before his final plate appearance, followed Jose Altuve, Dexter Fowler and Carlos Corporan, who reached in succession on two singles and a fielder's choice that loaded the bases.

Springer followed by chopping a 1-0 fastball from Charlie Furbush (0-3) toward the backpeddling Seager, who failed to field the ball cleanly as Altuve scored. That was just the fifth RBI on the season for Springer.

"This was obviously a big hit for me, I guess," Springer said. "I really didn't hit it that hard, but I'll take it. Hopefully this will slow me down, give me some confidence and just get back in there tomorrow and try to help us win again.

"I hit it and I saw it and I just said, 'Please get over his head.' I guess I hit it high enough just enough to hit off his glove. Then I saw him score and that was it."

Said Mariners manager Lloyd McClendon: "It was hit right at him. There's not a lot you can do about that. That's the way it goes. It's baseball."

Anthony Bass (1-0) earned the win for Houston (10-19) with two perfect innings of relief, capping a stellar night for the Houston bullpen.

Left-hander Tony Sipp, signed by the Astros earlier Friday, retired all five batters he faced in his first appearance with the club. He entered in the seventh inning with runners at the corners and two outs and induced a soft line drive back to the mound off the bat of Robinson Cano.

Three Seattle relievers piecemealed their way through the sixth and seventh innings before the Astros rallied against Yoervis Medina in the eighth. Left fielder Alex Presley worked a one-out walk, advanced to third on a Matt Dominguez single and scored when shortstop Jonathan Villar deposited a swinging bunt single down the first-base line.

Presley held at third on the play but scored when Medina stumbled toward the ball before finally opting to make the throw toward first, where he nipped Villar at the bag. That pulled Houston even at 4-apiece.

Jose Cisnero, Sipp, Chad Qualls and Bass then held firm until the Astros executed sublimely on offense before Springer delivered in the clutch.

"It definitely was a good overall effort," Astros manager Bo Porter said. "You look at those guys down there and we just continue to tell them when your name is called, come in and do your part. Don't try to do more than that. Just come in and do your part and tonight is a prime example of each one of those guys, from Cisnero to Sipp to Bass to Qualls, they just came in and did their part. And that's a great result."

Astros designated hitter Marc Krauss' RBI single in the third inning scored Fowler from second, doubling the Houston lead to 2-0. After the Mariners pulled even with a two-run home run from catcher Mike Zunino in the fifth inning, Krauss delivered an RBI single to right, scoring Jason Castro in the bottom of the fifth for a 3-2 Houston lead.

Houston right-hander Brad Peacock surrendered the lead immediately, allowing three of the first four batters to reach in the sixth before giving up a two-run single to Seager. He outlasted Mariners right-hander Felix Hernandez, who was battling illness and left after five wobbly innings.

"I still feel bad," Hernandez said. "I still have to go out there and do my job."

NOTES: The Astros announced the signing of LHP Tony Sipp, who received his release from the San Diego Padres after spending the first month with Triple-A El Paso. Sipp is 14-9 for his career with a 3.84 ERA over 304 games with the Cleveland Indians and Arizona Diamondbacks. He was 1-1 with a 4.30 ERA with El Paso. The Astros optioned RHP Paul Clemens to Triple-A Oklahoma City to make room for Sipp on the 25-man roster and transferred RHP Jesse Crain to the 60-day DL to make room for Sipp on the 40-man roster. ... Mariners RHP Hisashi Iwakuma will be activated from the 15-day disabled list and make his first start of the season on Saturday. Iwakuma finished third in the American League Cy Young Award voting last season and missed the first month of this season with a torn extensor tendon in his right middle finger. ... Mariners CF Abraham Almonte batted ninth for the first time this season, having spent 23 of his previous 24 starts hitting atop the order. He entered the weekend batting .204/.248/.301.