The Tigers will wait to see how Nathan feels Tuesday before scheduling a next step, possibly pitting him against hitters in a simulated game.
Nathan is eligible to be activated from the DL on Wednesday, but seems likely to need more time than that. Hours after his bullpen session Monday, Joakim Soria recorded his fifth save in as many chances in Nathan's place during the Tigers' 2-1 win over the Yankees. Asked how difficult of a decision he could face on who closes when Nathan comes back, Ausmus left it open.
"We'll worry about that when Nathan comes back," Ausmus said.
Rondon's return to the mound comes after three straight days of long-tossing. He had been shut down for about a week for further treatment on his biceps tendinitis, which flared up in his final days of Spring Training and landed him on the 15-day DL to begin the season.
"He's progressed, obviously," head athletic trainer Kevin Rand said. "Now he's back to throwing, he's back to stretching out, he's back to throwing long toss and he's just ready to make the phase into throwing off the mound."
Jason Beck is a reporter for MLB.com. Read Beck's Blog and follow him on Twitter @beckjason. This story was not subject to the approval of Major League Baseball or its clubs.