SEATTLE -- As the Mariners come off a tough 12-game East Coast road trip and open a nine-game homestand on Friday against the A's, they'll have some welcome reinforcements arriving, as September callups will be eligible to join the expanded rosters for the final month of the season.
Seattle intends to take full advantage of that roster allowance to bolster an injury-challenged pitching staff and add some backup position players as well.
"A fair amount," general manager Jerry Dipoto said when asked how many callups will be added. "We'll make some moves in waves, like we did last year. There'll be a small group added on Sept. 1, then as [Triple-A] Tacoma's season draws to a close [on Monday], there'll be a few more.
"We'll add a couple position players, but predominantly we'll expand our pitching staff."
Most of the new names will be familiar to those who've followed a Mariners team that has already used a club-record 55 players this season, including 37 pitchers. Those numbers will expand by one on Friday, when newly acquired pitcher Mike Leake arrives. He'll become the 17th starting pitcher employed this year.
"Most of the guys that will be back are guys that you've seen at some point during the season," manager Scott Servais said. "They've been up for different stints, filling in for injured players. Certainly we need to add to our pitching staff -- getting a few more guys in the bullpen to kind of stretch out some of the outings we've had. Some of the guys are tired and are hanging a little bit right now. So [there will be] welcome additions there."

Center fielder Jarrod Dyson is expected to be activated off the 10-day disabled list Friday after missing two weeks with a strained groin muscle. Because of the expanded rosters, he can now return without needing to send another outfielder down.
Most of the callups figure to already on the 40-man roster, which is now full with the addition of Leake. For every non-40-man roster player added, someone will have to be designated for assignment off the 40-man to make room, so that will limit some of the additions.
Available pitchers on the 40-man roster include Sam Gaviglio, Andrew Moore, Max Povse, Chase De Jong and Thyago Vieira, who've all pitched at various times for Seattle this season. Reliever Dan Altavilla will definitely be brought back, but he'll need to wait 10 days from when he was optioned back to Tacoma on Monday.

The club could also bring veteran reliever Evan Scribner (flexor bundle strain in right elbow) off the 60-day disabled list, as he's recently returned from an elbow issue that has sidelined him since April. Shae Simmons (right flexor strain) is a similar candidate to come off the 60-day DL, though his availability has been spotty due to recurring issues.
As for position players, the club is expected to add Mike Marjama as a third catcher. He's not on the 40-man roster, but he was acquired from the Rays by trade in July. The 28-year-old has only hit .169 in 20 games for Tacoma, but Marjama was a Triple-A All-Star for Durham in the Tampa Bay organization, and he would provide some insurance behind Mike Zunino and Carlos Ruiz for the final month.
First baseman Daniel Vogelbach is on the 40-man roster and could be added as well.
Not expected to be activated is utility man Shawn O'Malley, who missed much of the season while recovering from an appendectomy and then shoulder surgery. O'Malley was back playing for Tacoma this past month, but he suffered a concussion when he tripped over the mound and banged his head while tracking a popup.
"Shawn has gone through a lot this season, between the shoulder issue and there's been a ton of different things that have come upon him this year," Servais said. "So I don't know what kind of status he's in game-shape or if he can really help us.
"I think you're looking for guys that can come off the bench or spot start for a day here or there. Everybody is in play right now, we're just trying to decide what the best fit is for our club."