SEATTLE -- Franklin Gutierrez will be disappointed to see the Padres leave the schedule.

"I think we need to play these guys more," Seattle's center fielder said.

Finding a recent power surge against the Padres, Gutierrez led off the eighth inning with a solo homer off reliever Edward Mujica, and the Mariners won their 19th one-run game of the season, 4-3 over the Padres on Wednesday night.

It was Gutierrez's fourth homer in five games against the Padres this season. He hit three homers last week when the teams played at Petco Park. Two of those homers came in a loss to the Padres.

This time, Gutierrez came through with the game-winner.

Ahead in the count 2-0, Gutierrez lined Mujica's fastball over the left-field wall, barely clearing the yellow stripe in front of the Mariners' bullpen for his seventh homer. He was the first batter to go deep on Mujica (2-3) since June 6, when Arizona's Justin Upton homered off the Padres' eighth-inning setup man.

"He got behind in the count and threw a fastball to a fastball hitter," Padres manager Bud Black said. "He squared it up. That happens."

Russell Branyan added his 18th homer of the season in the second inning for Seattle, a three-run shot that erased the Padres' early 2-0 lead. While his two-run homer on Tuesday barely cleared the wall, there was no doubt about this 418-foot shot to center off starter Josh Geer. It was the 17th homer allowed this season by Geer.

"You never want to give up home runs, especially three-run homers. Those kill you," Geer said.

Seattle has won six of its last eight overall and improved to 19-13 in one-run games this season.

But this victory came with a cost. Seattle likely lost shortstop Yuniesky Betancourt for at least two weeks after he injured his hamstring running out a ground ball in the eighth inning. Manager Don Wakamatsu said Betancourt would have an MRI today but is likely headed for the disabled list.

Sean White (2-0) picked up the victory working the eighth, getting Scott Hairston to pop out to end the inning with Tony Gwynn Jr. at second base. David Aardsma pitched the ninth -- including striking out slugger Adrian Gonzalez -- for his 15th save in 16 chances.

Kevin Kouzmanoff gave the Padres a 2-0 lead with his 10th homer in the second inning. After fouling off three straight 3-2 pitches, Kouzmanoff lined Morrow's ninth offering over the out-of-town scoreboard in deep left field.

After loading the bases in the first and getting a key putout at the plate when Hairston threw out Betancourt trying to score in the second, Geer settled down.

Following Betancourt's double in the third -- which missed being a homer by about a foot -- Geer retired nine of the final 10 batters he faced, allowing a walk to Betancourt in the sixth.

Morrow continued his transition from reliever to starter. On a pitch limit of 95, Morrow finished five innings having thrown 87, walking one and striking out four. But he missed out on a chance at his first win of the season when the Padres pieced together a run in the fifth.

Hitting just .115 entering the game, Will Venable had a one-out single, followed by Eliezer Alfonso's single. After Morrow struck out Everth Cabrera, Gwynn singled to left to score Venable.

Padres notes

The club announced that it has agreed to terms with nine more picks from the recent amateur draft, including third-rounder Jerry Sullivan, a pitcher from Oral Roberts. The Padres have now agreed to terms with 31 of their 50 picks, including six of the top 10. … Terry Kennedy, the manager of the Padres' Double-A affiliate in San Antonio, was picked as a coach for the U.S. team in the All-Star Futures Game. The game featuring many of the top prospects in the minors will be played July 12 in St. Louis, two days before the major league All-Star game. Hall of Fame shortstop Ozzie Smith will manage the team.