OAKLAND, Calif. -- Jesse Hahn struggled through spring training and was sent to the minors to work things out.

On Saturday, he displayed he did that.

Hahn pitched 6 2/3 shutout innings in his first start with the Oakland Athletics and Billy Burns provided just enough offense to help the A's down the Houston Astros 2-0 on Saturday.

"That's the best stuff I've had all year," Hahn said. "I was throwing strikes, that was the most important thing, strike one and being able to put hitters away."

It also helped that part of the Astros' game plan was to attack Hahn early in the count.

"He tries to get ahead of hitters with his fastball," Astros manager A.J. Hinch said. "The risk and reward of that was they were able to get some quick outs. We couldn't get the ball in the air. He pounded us in and broke a few bats. He had nasty stuff."

Josh Phegley and Marcus Semien each walked and had a hit for the A's, who won their fourth straight at home after opening the season 1-7 in the Coliseum.

Hahn (1-0), who opened the season at Triple-A Nashville following a tough spring, showed he belonged as he allowed one baserunner to venture past first base. He gave up three hits, walked two and struck out four as the A's ended the month over .500 at 13-12.

"I was able to put it over for strike one and get ahead right away, and when I needed it down I was able to do that," Hahn said. "It keeps my tempo there, keeps me working fast, and I'm at my best when I'm working fast."

John Axford went 1 1/3 scoreless innings and Ryan Madson worked the ninth for his eighth save in as many chances. The A's recorded their first shutout of the season and the Astros were shut out for the first time.

The Astros loaded the bases with one out in the ninth. Jose Altuve and Carlos Correa drew walks and Colby Rasmus, in 10-pitch at bat, fought off some tough pitches before blooping a single into center field.

Madson then got Evan Gattis to ground into a game-ending double play.

Chris Devenski (0-1) pitched effectively enough to win most games, hampered by a spell of wildness in one inning. He allowed two runs on five hits over five innings in his first major-league start.

"My command wasn't there in the second inning," Devenski said. "I fell behind hitters and had a lot of 3-2 counts. I had to bear down to get out of that. It's something to build on."

Devenski walked three, all in one inning, and struck out four.

Correa doubled off the wall in the seventh, the hardest hit of the game for the Astros, who have lost seven of nine and ended April with a 7-17 mark.

Hahn retired 10 in a row at one point and left after walking Gattis with two out in the seventh. He faced the minimum of 15 batters through the first five innings.

After Hahn walked George Springer in the first, he induced Correa to hit into a double play.

Preston Tucker singled to open the third before Luis Valbuena hit into a double play.

Of the first 15 outs recorded by Hahn, 13 were recorded on grounders, a clear sign that his sinker was effective.

"I don't know that I've seen him better than that," A's manager Bob Melvin said. "Velocity, movement, mixed his pitches, throwing his curveball for a strike, mixing in a changeup, and you're throwing 96, 97 mph and throwing strikes. About as good as we've seen him."

Devenski, meanwhile, showed signs of being an efficient starter for the Astros and also struggled at times.

After striking out Chris Coghlan and retiring Coco Crisp on a weak comebacker, Devenski gave up a double to Friday night's hero Yonder Alfonso and walked No. 8 and No. 9 hitters Josh Phegley and Marcus Semien ahead of Burns' two-run single.

In the fourth, the A's had runners on first and third with one out before Devenski retired Burns on a short fly ball and Jed Lowrie on a grounder.

NOTES: A's RHP Chris Bassitt has a partial UCL tear in his right elbow, which was revealed by a MRI exam performed Friday. The diagnosis could lead to season-ending surgery. Bassitt is going to Cincinnati for a second opinion. ... RHP Andrew Triggs was optioned to Triple-A Nashville to make room for RHP Jesse Hahn. Triggs spent one day with the A's and did not pitch. ... INF Danny Valencia (hamstring) is on track to rejoin the A's when they head to Baltimore to open a series on Friday, May 6. He's expected to make three rehab starts this week. ... INF Eric Sogard (sore neck) is continuing his rehab. ... Astros OF Carlos Gomez will miss a couple of days because of a sore left ribcage. He sustained the injury diving for a ball Friday night. Gomez left Wednesday's game in Seattle early when he was hit by a pitch on his right hand. ... RHP Ken Giles, while never officially announced as the Astros set-up man, will not necessarily get the ball in the eighth inning for the time being. "I want to give him a physical and mental break," Astros manager A.J. Hinch said a day after Giles recorded his first blown save of the season. He's 0-2 with a 9.00 ERA this season, although he's 9-6 with a 2.15 ERA over 124 career relief appearances. ... RHP Chris Devenski was the first Astros pitcher this season to make his first major-league start. RHP Nick Tropeano was the last to win in his starting debut in 2014.