To make room for Young and Plouffe on the roster, catcher Rene Rivera and outfielder Rene Tosoni, who had two hits and an RBI in Sunday's 6-3 victory, were optioned to Rochester.
Young, on the disabled list since June 26 with a sprained right ankle, played in a doubleheader on Saturday, going a combined 2-for-6 with a walk while playing seven innings in left field. He went 1-for-2 with a two-run homer on Sunday, and finished his nine-game rehab stint with a .290 batting average, two homers and three doubles.
"Tosoni needs to go play," Gardenhire said. "He's a nice-looking young player, but Delmon's going to play every day. [Ben] Revere's going to play in center and [Michael] Cuddyer and whoever else will be playing right a lot, so he needs to go down there and get some more swings, and we'll see where we're at here in a couple weeks."
Plouffe, meanwhile, has been impressive at the plate with Rochester. He had a .313 batting average and 1.019 OPS in 51 games with 15 homers and 11 doubles after going 1-for-4 on Sunday. He's also played all over the diamond recently, as the shortstop has seen time at first base, second base, third base, left field and right field.
Plouffe, who struggled defensively during his 18-game stint with the Twins earlier this year with three errors, has been playing first base with Rochester since Tuesday.
"He's doing fine with no problems," Gardenhire said. "He's played well everywhere he's been down there. He's confident, which is a big thing for me, because he fought it so much when he was up here."
Rivera, meanwhile, hit .181 with a home run and four RBIs in 27 games with the Twins, but became expendable with the return of Joe Mauer and emergence of Drew Butera, who is hitting .311 over his last 20 games.
Tosoni had a .205 batting average and two homers in 26 games with Minnesota, but fared much better recently, hitting .304 over his last six starts in the left field.
"He said he enjoyed me being here," Tosoni said of his talk with Gardenhire. "It's just we've got so many outfielders we had to make a move. It was fortunate for me to be here just because of injuries. But I've had a good time being up here and I'm glad about the opportunity."