With Miguel Batista and Chris Young nearing returns from the disabled list, Collins said Hefner is not a lock to make his next scheduled start Monday, but he could fill in for Dickey against the Cardinals on three days' rest Saturday if the expected rain arrives.
"We are going to watch the weather very closely for tomorrow and see what it's going to be," Collins said. "If we're going to play in a downpour tomorrow, we have to decide whether or not that's the best conditions for R.A. to go out in."
Collins said Young may have made his last rehab start after pitching six scoreless innings for Triple-A Buffalo on Thursday, and Batista is eligible to return Monday. He will not use a six-man rotation once the pair returns, instead choosing between the two and Hefner for the final rotation spot.