DETROIT -- A decision on rehabbing pitcher Dontrelle Willis is coming soon.

After making his third Minor League rehabilitation start at Triple-A Toledo on Saturday night, Willis threw a bullpen session under the watchful eye of Tigers pitching coach Chuck Hernandez before Tuesday's game against the Mariners at Comerica Park. The session, which lasted about 10 minutes, was the latest step in the left-hander's return from a hyperextended right knee.

The knee apparently feels strong, but the club is looking at control issues that have plagued Willis through Spring Training and early this season. It's unknown whether Willis will return to his spot in the Tigers rotation this week or make another start in Toledo.

"We're going to make a decision on him in the next few days," manager Jim Leyland said Tuesday afternoon.

The Tigers have plenty of time. They have about two weeks remaining in Willis' 30-day rehab assignment to make that decision.

In three starts with the Mud Hens, Willis, acquired in the December trade that also brought Miguel Cabrera to Detroit, went 1-1 with a 4.41 ERA, allowing eight earned runs in 16 1/3 innings. He has 11 strikeouts against seven walks, though four of them came in his last rehab start against Columbus.

Willis injured his knee when he slipped on the mound on April 11 against the White Sox, his second start of the year. In his first start, he allowed three earned runs on one hit in five innings, but also walked seven.