"We think it's a smart move to let him focus on just the Sprint Cup action this weekend," Busch said.
Keselowski pulled out a gutsy victory Sunday at Pocono, holding off Kyle Busch over the final laps despite a fractured left ankle and strained back suffered a week ago in a crash while testing at Road Atlanta.
It was Keselowski's second win of the season and moved him into strong contention for the Chase for the Sprint Cup championship. But Keselowski, last season's Nationwide champion, is still ailing as he prepares for Sunday's Cup road race on The Glen's grueling 11-turn layout.
"Penske Racing is fortunate that Kurt ... is in its stable of drivers," team president Tim Cindric said. "We appreciate him lending a hand during this time. We will continue to monitor Brad's recovery."
Cindric said Keselowski's Nationwide schedule will be determined on a race-by-race basis.
The last time Kurt Busch drove a Nationwide race at The Glen, he held off Robby Gordon in a fender-bending final two laps for the win in 2006.