LeBlanc will get the start Friday for the Padres, who open a three-game Interleague set against the Oakland A's at PETCO Park.
LeBlanc is 1-4 with a 4.08 ERA with Portland. He was up briefly with the Padres recently, but didn't pitch.
It appears San Diego will make another move to fill the void in its rotation Saturday with Walter Silva the likely candidate to start against the A's.
Black said that Young will likely miss two starts after experiencing soreness in his shoulder his past four starts, including in Anaheim on Sunday, when he allowed five walks over 2 1/3 innings, including four consecutive walks at one point.
Black indicated that Young, who is 4-6 with a 5.21 ERA, wouldn't likely need "a lengthy rehab."
The Padres are now without the top two starting pitchers in their rotation, as Jake Peavy went on the disabled list on Saturday with tendon damage in his right ankle, leaving him with a cast on his ankle.
Peavy will wear the cast for a month and have the ankle reevaluated. He's not expected back until after the All-Star break at the earliest, though there is speculation that Peavy might not return until August or later.
"You lose your top two starting pitchers, it's not a scenario that you look forward to," Black said. "You look across the land ... [the D-backs' Dan] Haren-[Brandon] Webb, [the Giants' Tim] Lincecum-[Matt] Cain, [the Dodgers' Chad] Billingsley-[Clayton] Kershaw ... you take two guys out of a rotation, and it's tough.
"But guys are going to be getting an opportunity to see what they can do as Major League pitchers. We're going to see what our depth is."
Corey Brock is a reporter for MLB.com. This story was not subject to the approval of Major League Baseball or its clubs.