MINNEAPOLIS -- Right-handed reliever Carter Capps is undergoing a steep learning curve in the Majors, but manager Eric Wedge would like him to throw a few more curves of his own to go along with the upper-90s fastball that figures as his calling card.

Capps, 22, made his seventh appearance on Wednesday and equaled his longest outing yet with two innings of work in relief of Jason Vargas. But 36 of his 39 pitches were fastballs and the Twins timed him up well enough to rack up three runs on four hits in his final inning as his ERA ballooned to 5.87.

"It should have been a good experience for him," said Wedge. "He was able to throw 35-40 pitches, but he has to use all his pitches. That was just way too many fastballs. He has a great fastball, but up here these big league hitters, it doesn't matter how hard you throw, they can turn it around."

Capps came in with one on and two out in the fifth and got Trevor Plouffe to line out to short, though it took him nine pitches. Two of those were curves, which Plouffe fouled off.

The hard-throwing right-hander needed just six pitches to retire the side in the sixth, all fastballs in the 98-mph range. But things got difficult after that.

He fired eight straight heaters at Joe Mauer leading off the seventh, including one that hit 100 mph, with the Twins catcher fighting him off and finally turning around a 98-mph offering and tripling over the head of Chone Figgins in center.

Capps used just one curveball the rest of the inning, with Josh Willingham driving it for a sacrifice fly to score Mauer, and then threw nothing but fastballs with his final 14 pitches -- giving up three hits to the next four batters -- before Wedge brought in Lucas Luetge.

"He's got a good breaking ball and a changeup he can utilize, especially to left-handers," Wedge said. "So hopefully he learned something."

Saunders expected back in Mariners lineup Friday

MINNEAPOLIS -- Michael Saunders had hoped to get back into the lineup at some point this week against the Twins, but the Mariners outfielder instead is pointed toward returning when Seattle opens a nine-game homestand Friday against the Angels at Safeco Field.

Saunders sat out his sixth straight game on Thursday since straining his right groin muscle in a ninth-inning collision with Eric Thames in the outfield in last Friday's 9-8 loss to the White Sox at U.S. Cellular Field.

Manager Eric Wedge said Saunders was very close to being ready, but the decision was made to give him one more day to make sure he's 100 percent to go on Friday night.

"We just feel like he needs a day of rest, he's been pushing so hard to come back," Wedge said prior to Thursday's finale with the Twins. "The best opportunity for him to play in the outfield tomorrow and play an entire game would be to give him some time today. We plan on him being in the outfield tomorrow."

Franklin Gutierrez was back in center field for Thursday's 10:10 a.m. PT getaway game after sitting out Wednesday's 10-0 loss to rest his legs as he eases his way back from a two-month absence following a concussion.

"He should be fine," Wedge said. "We'll just keep an eye on his schedule and an eye on him and work him back in. He said he had some Spring Training legs going, so we just didn't want to push that. It's been an odd year for him, through no fault of his own. We'll give him days here and there."

September callups to bolster roster soon

MINNEAPOLIS -- Mariners manager Eric Wedge said the club would probably bring up one or two players from Triple-A Tacoma on Saturday, the first day rosters can be expanded with September callups, with more to arrive after the Rainiers season ends on Monday.

One of the additions will be first baseman Mike Carp, who is currently on a rehab assignment as he recovers from a strained groin muscle. Carp felt some tightness in the leg during a swing and was taken out of Tuesday's game and sat out Wednesday in Las Vegas, but is expected to play Thursday.

The Rainiers also have a number of players who spent time with the Mariners at various points this season, as well as some prospects who will get their first look.

"There are a few guys who were here quite a bit of the year we want to get back up, and a few of the younger guys we want to put our eyes on, even if they're not playing a great deal, just to have them up here in this environment," Wedge said. "I think that's healthy and part of the progression, which is important."

Wedge wasn't naming names, but among the current Rainiers players who've been with Seattle at times this season are outfielders Casper Wells and Carlos Peguero, infielder Alex Liddi, reliever Shawn Kelley and starters Erasmo Ramirez and Hector Noesi.

Danny Hultzen, the first-round Draft pick in 2011, is the highest-profile prospect with the Rainiers, but he's struggled down the stretch and saw his record fall to 1-4 with a 6.09 ERA after giving up six hits, six runs and five walks in 2 1/3 innings Wednesday in Las Vegas.

"It's his first year of pro ball. He goes right to Double-A and did great," Wedge said. "Triple-A is a little different level. We didn't expect him just to run straight through everything. It's just too hard. I know he's learning a great deal down there.

"It's toward the end of the year and I'm sure he's feeling it a little bit with a long year, but he's had a lot of success, he's impressed a lot of people. Sometimes you learn more from those tough outings than anything else. With his mindset and maturity level, he's going to be fine."

Worth noting

• Seattle musician Macklemore, who performed the "My Oh My" tribute to Dave Niehaus after the Hall of Fame broadcaster's death in 2010, will throw out the ceremonial first pitch at Friday's 7:10 p.m. game against the Angels at Safeco Field.

• Just as a reminder to fans, Wednesday's game against the Red Sox will start at 7:10 p.m., a switch from the 12:40 p.m. start listed on pocket schedules that were printed before the start time was switched.

That game is now a night contest, while the season finale on Oct. 3 against the Angels has been flipped to a day game at 3:40 p.m.

• With one game still remaining in August, the Mariners already have guaranteed themselves a winning record for a second straight month for the first time since 2009, when they finished the season with four straight months over. 500.