SEATTLE -- Clint Frazier has spent the better part of the last two months working on his defense at Triple-A Scranton/Wilkes-Barre, and it appears that the outfielder's reward will come in the form of a September callup.

Yankees manager Aaron Boone said that the club has not finalized its decisions for the Sept. 1 roster expansion from 25 to 40 players, but he strongly indicated that Frazier is among those who can expect a big league promotion.

"I think there's a couple of obvious ones, but we'll talk through exactly how many we wind up doing," Boone said. "I think Frazier will probably be here."

Frazier, who turns 25 in September, batted .283/.330/.513 with 11 homers and 34 RBIs in 53 games for the Yankees this season. He entered play on Wednesday having batted .243/.300/.426 with seven homers and 23 RBIs in 57 Triple-A games.

While in the Majors, Frazier saw the majority of his time in right field, including a June 2 contest in which he misplayed three balls in a loss to the Red Sox. Frazier has said that his inconsistent fielding is what has kept him in Triple-A since his most recent big league contest on June 16.

“All my energy is going into being a defender, because if I’m fortunate to get that call back, man, I want to be in the outfield and turn heads and people be like, ‘Wow, this guy has been working down there,’” Frazier told The New York Times earlier this month.

Boone has said that the Yankees expect to recall right-hander Jonathan Loaisiga shortly after rosters expand. Other callups on the 40-man roster could include right-handers Chance Adams, Ryan Dull and Adonis Rosa, catcher Kyle Higashioka and infielder Breyvic Valera.

Off to the desert

Five Yankees farmhands have been invited to participate in the Arizona Fall League, with rosters having been announced on Wednesday.

Right-handers Daniel Bies and Glenn Otto, catcher Donny Sands, first baseman Brandon Wagner and outfielder Josh Stowers will play for the Surprise Saguaros.

None of the five are currently ranked among the Yankees' Top 30 prospects by MLB Pipeline.

Scranton-bound

Luis Severino and Jordan Montgomery will both join Scranton/Wilkes-Barre this weekend, with Montgomery scheduled to make his second Minor League rehab start on Friday against Buffalo. Severino will make his first Minor League rehab start on Sunday, also against Buffalo.

Weather concerns are pushing the hurlers north from Florida, where Montgomery made his first start with Class A Advanced Tampa. Boone had suggested that Severino might pitch for Double-A Trenton, but said on Wednesday that the club decided the field conditions would be better at the Triple-A stadium.

"It's what makes the most sense in building [Severino] up the right way so he can impact us the most down the stretch and hopefully into the postseason," Boone said. "The idea is that he will go a couple of innings, 35 pitches, probably throw another 10 pitches following the game to build him up. Then we'll see what we do from there."

Trainer's office

Cameron Maybin (left wrist soreness) returned to the Yankees' lineup for the first time in four games on Wednesday, and Didi Gregorius is not far behind. Gregorius sustained a bone bruise behind his right shoulder on Sunday, when he was hit by a Clayton Kershaw fastball. Boone said that he expects Gregorius to be in the Yanks' lineup on Friday.

"I feel like he continues to make progress," Boone said. "His throwing was really good [Tuesday]. From the volume standpoint, he's able to do a lot of hitting. There was still that soreness there, so with the off-day [Thursday], I felt like this is the best way to go."

Comeback trail

Dellin Betances (right lat strain) threw to hitters on Wednesday at the Yankees' complex in Tampa, Fla., and Boone said that it "went pretty well." Betances is scheduled to throw to hitters again on Saturday.

Thairo Estrada (right hamstring strain) has resumed running and throwing.

Giancarlo Stanton (right PCL strain) is "probably getting pretty close" to facing live pitching, Boone said. The club has not determined where or when that will occur. Stanton took on-field batting practice Tuesday, the first time he has done so since sustaining his injury on June 25.

Stephen Tarpley (left elbow impingement) has resumed his throwing program and is close to throwing from a mound, Boone said.

This date in Yankees history

Aug. 28, 1977: Celebrating his 27th birthday, Ron Guidry fired his third shutout of the season in a 1-0 victory over the Rangers. "Louisiana Lightning" permitted two hits and faced one batter over the minimum. Graig Nettles tripled and scored on Reggie Jackson's single for the game's only run.