Jordan Montgomery returned, too, though he likely is tuning up for next season.
Betances faced two batters and struck out both Sunday in a 6-4 loss to the Toronto Blue Jays that ended a 10-game road trip, New York's longest this season.
"To have him come out and be as sharp as his command as he was encouraging," manager Aaron Boone said. "Hopefully he can put himself in a position to be an impact guy for us moving forward."
A 31-year-old right-hander, Betances was diagnosed with an impingement in his pitching shoulder after his fourth spring training appearance on March 17. His rehabilitation stopped when the team said June 11 that he had strained his right latissimus dorsi muscle, and Betances did not start a minor league injury rehabilitation assignment until September.
After three minor league outings, Betances entered to start the fourth inning and threw seven of eight pitches for strikes. He struck out Reese McGuire on a 95 mph fastball and got Brandon Drury to take three straight strikes, the last an 84 mph curveball.
Betances hopped off the mound after the second out, mistakenly thinking it was the end of the inning.
"I knew I only had a couple of hitters," Betances said. "That's why I got a little excited out there."
Betances said he was "a little nervous" about pitching with just one day of rest in between appearances.
"My arm speed is still not where I want it to be, so I've got to attack the strike zone and change speeds, and I was able to do that today," he said.
New York hopes Betances will be a factor in the playoffs, joining an already strong bullpen that includes Aroldis Chapman, Zack Britton, Adam Ottavino, Tommy Kahnle and Chad Green. Betances also hopes to show he is at or close to full strength going into an offseason in which he is eligible for free agency.
Catcher Austin Romine said Betances looked "pretty close" to peak form.
"His slider had some good depth and his heater had something behind it," Romine said. "Pretty encouraging stuff when you see that, especially the swings they were taking."
Ace starter Luis Severino, also sidelined since spring training by a lat strain, is slated to make his first big league outing this season when the Yankees open their final homestand Tuesday against the Los Angeles Angels.
Green pitched the first inning against the Blue Jays and Montgomery followed in his first major league appearance since May 1 last year, when he left a start at Houston after one inning. The 26-year-old had Tommy John surgery on June 7, 2018.
Showing a velocity in the low 90 mph range, Montgomery allowed three runs and four hits in two innings. He threw 26 of 41 pitches for strikes.
"Monty looked pretty good," Boone said. "I thought his breaking ball wasn't real sharp, although I thought he finished strong with it."
Aaron Judge's 23rd homer had put New York ahead in the first against Wilmer Font, but Montgomery gave up an RBI single in the second to former Yankee Billy McKinney, who scored on a double by Richard Ureña before Montgomery struck out Bo Bichette to end the inning.
DJ LeMahieu hit an RBI double and scored on Didi Gregorius' single for a 3-2 lead in the third against T.J. Zeuch (1-0), but Randal Grichuk tied the score in the bottom half with the first of his two homers, then hit a three-run drive in the fifth off Nestor Cortes Jr. (5-1). Grichuk has a career-high 28 homers this season.
New York headed home with a 98-53 record, and its magic number for clinching a postseason berth remained at two. The Yankees had won their 10 previous series rubber games since an April 14 loss to the Chicago White Sox.
"The kind of success we've had in being able to run off series, it's a difficult thing to do," Boone said.
Zeuch, who debuted on Sept. 3, allowed three runs - two earned - five hits and three walks in 5 1/3 innings. He retired 11 of his final 13 batters.
"I thought I made a lot more competitive pitches," Zeuch said. "I stayed out of the heart of the plate."
Ken Giles finished for his 20th save in 21 chances as Toronto won consecutive home series for the first time this season. The Blue Jays took two of three from the Red Sox last week and are 31-44 at home.
Yankees: Betances and Montgomery were activated from the 60-day IL. RHP Jonathan Holder (shoulder) was transferred to the 60-day IL and RHP Ryan Dull was designated for assignment.
Blue Jays: 3B Vladimir Guerrero Jr. and 1B Justin Smoak got the day off.
SEE YA, CC!
Before the game, the Blue Jays honored retiring Yankees LHP CC Sabathia with a video tribute and on-field ceremony. Blue Jays president Mark Shapiro, Cleveland's GM during Sabathia's tenure with the Indians, presented the pitcher with a painting before the two embraced.
New York went 6-4 against Boston, Detroit and Toronto on its 10-game trip.
Judge's homer was New York's 286th this season, matching Minnesota for the big league record. The Twins hit three Sunday.
Blue Jays: Toronto starts a three-game series at Baltimore Tuesday.
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