SEATTLE -- Since moving to first base a couple of weeks ago, Jose Lopez is starting to hit like a first baseman, bashing home runs in bunches.

He hit two of them on Friday night against the Athletics, hiking his single-season high to 17, to lead the Mariners to a 10-8 victory in front of 24,662 on Fan Appreciation Night at Safeco Field.

Rookie catcher Rob Johnson hit his first career home run, a two-run blast into the visitor's bullpen in left-center, and sprinted around the bases instead of enjoying the jaunt with a trot.

"As soon as I hit 100 or so," he said, "I might slow down. But that's how I run out my home runs."

On a night that right-hander Brandon Morrow struggled with his command, the Mariners needed a robust offense to get past the Athletics. A pair of five-run innings, in the third and fifth innings, provided enough runs for Morrow, a converted reliever, to pick up his third win of the season and second in a starting role.

Asked to evaluate his second full season in the Major Leagues, Morrow said, "I thought I did a great job relieving, and the transition process to starter has started. Every outing is a learning experience. A lot of good things, and a lot of bad things, have happened in my starts."

When he has command of his pitches, throwing strikes and keeping it down, he seems unhittable. But when he gets out of sync, he runs into wild streaks where walks come in bunches and his pitch count soars.

He needed 114 pitches to get 15 outs on Friday night.

"No one is more aware than he is that he can't throw that many pitches in a short amount of innings," manager Jim Riggleman said. "He continues to show electric stuff, but he walks people and gets behind hitters. The guys with power will hurt you if you get behind them."

Morrow fell behind in the count to Jack Cust in the second inning and surrendered a 403-foot solo home run to right field that shook up the people eating at the Hit it Here Café. He fell behind Travis Buck in the fourth inning and surrendered a two-out, three-run shot that wiped out a 5-2 Seattle lead.

He wobbled again in the fifth, walking one and surrendering a pair of one-out singles before getting a visit from Riggleman.

Some thought that the manager went out to make a pitching change. But he stuck with the starter.

"There were some things that went into it," Riggleman said.

The bullpen was a little short on arms because of recent work and the goal was to get Morrow through the fifth inning, so he could at least qualify for a win if the Mariners scored in the bottom of the inning to take the lead.

"I was letting him know that I was not going to give him too much more rope on this leash," Riggleman said.

Morrow retired the next two hitters to keep the score at 6-5, a deficit the Mariners erased with their five-run fifth, and called it a night -- and a season.

The sudden power surge by Lopez, who dialed long distance twice in the same game for the second time this season, is basically a story of a maturing hitter.

"Power is the last thing that comes in a player's development," Riggleman said. "It's coming with Jose. I am not expecting him to go out there next season and hit 25 home runs, but he will hit 20 just by being himself.

"He's a good hitter, can drive the ball into both gaps, has a good two-strike approach and is not afraid to hit with men on base."

Lopez extended his hitting streak to four games, going 6-for-17 with five RBIs and ranks third among American League second basemen in home runs. He also leads his colleagues with 89 RBIs.

His other two-homer game of the season (and his career) occurred on Sept. 7 against the Yankees.

Prior to this season, Lopez's single-season high in home runs was 11 last season. He hit 10 in 2006 and his Minor League high was 13, in 2003 and '04.

"I don't know," Lopez said when asked where the power surge has come from.

"I am not looking for homers, I am looking to hit the ball hard."

Right-hander Mark Lowe provided the Mariners with some solid relief. He replaced Morrow and worked the sixth, seventh and eighth innings, holding the Athletics to two hits and one run.

Roy Corcoran pitched the ninth inning and recorded his third save of the season.

"I didn't want to use Corcoran," Riggleman said. "He was in three of the last four games and was up in the game he didn't get in."