MINNEAPOLIS — The last six weeks certainly have been fun and interesting for the Mariners, winning games far from the glare of AL West contention. Think anyone outside Seattle and Minnesota fandom cared that a dropped fly ball by Twins left fielder Josh Willingham and Justin Smoak's did-he-tag-him-or-didn't-he play on Ben Revere for the last out helped the Mariners win again Thursday?

Maybe not, but winning three of four at Target Field against the stumbling Twins — after three straight one-run losses to the White Sox in Chicago — sets up the final 30 games of the season to determine whether the Mariners have the foundation of a good team.

Willingham's error contributed to a four-run sixth inning for the Mariners, whose bullpen squandered two-thirds of a three-run lead before Tom Wilhelmsen finished the 5-4 victory with a tense 21st save. Wilhelmsen left two men on, escaping when first baseman Smoak tagged out speedster Revere on a nubber near the line. Revere contorted his upper body and ran out of the baseline trying to avoid Smoak's glove.

"I barely got him. Barely," Smoak said. "I barely nicked his uniform."

On a sunny, sweltering afternoon, that was enough.

Beginning with Friday's homestand opener against the Angels, the Mariners have 21 games remaining against division opponents. The Red Sox, Orioles and Blue Jays fill out the rest of the schedule.

September can be deceiving with young players, but manager Eric Wedge sees this as a proving ground for the kids in his clubhouse.

"When you get into July and August, this is when it really gets real," Wedge said. "This is when the good teams really turn it up a notch, really start to sniff it out. We're right in the middle of that.

"We have a lot of guys playing in spots they haven't played before. Some of these guys, it's their first big-league season. Some of the guys, it's their first full big-league season. That's different when it comes to September. Turn the page to September, and now you start really focusing on what you can do here."

Thursday, the Mariners showed some of that.

Starter Blake Beavan (9-8) recovered from a two-run first inning to hold the Twins scoreless on two hits over the next six innings, relying more on his curve and changeup than his fastball.

"The big thing for me today is I threw my changeup a lot," Beavan said. "I think it was the most I've thrown my changeup since I've been in the big leagues, at least eight to 10. It got me a bunch of quick outs, and I kind of took it from there."

Kyle Seager contributed an RBI single in the first, following a double by Franklin Gutierrez, and a bases-loaded, game-tying sacrifice fly in the sixth.

That sixth inning turned big when Willingham mishandled Jesus Montero's subsequent sacrifice fly. Willingham did not watch the ball into his glove and it glanced off the webbing. With two out, Trayvon Robinson delivered a two-run single to make it 5-2, runs that proved important in the eighth when Willingham pulled his second homer in two days with a man on against Stephen Pryor.

Wilhelmsen walked the tying and winning runs on in the ninth, and pinch-runner Darin Mastroianni made things even more tense by stealing second with one out, and then third with two out. Then Smoak turned Revere's dribbler into the final out, a calm play that showed the maturation Wedge sees in his players.

"Their heartbeats are a lot better," Wedge said.

"They're much more experienced. They're doing a better job in step-up opportunities. (Minnesota) gave us an opportunity (on Willingham's error), and our guys did a good job taking advantage of it. That's what you have to do if you're going to win ballgames up here."

Especially against good teams in September.

"We have a strong division, and we feel like we're right in the mix of it," Seager said. "It will be good for us to play those guys."

Note

• Wedge expects Michael Saunders (groin strain), who missed his sixth consecutive game Thursday, to start in the outfield on Friday at Safeco Field.

"He's pretty much there," Wedge said.