Promising pitcher Zack Wheeler is expected to be promoted from Class AAA Las Vegas sometime in June. But whose spot in the rotation would he take?

It has been assumed Wheeler would squeeze out fifth starter Jeremy Hefner. Not so fast, manager Terry Collins said before the Mets' 7-5, 10-inning loss to Atlanta in the completion of a suspended game.

"Jeremy Hefner certainly could be a guy who stays in this rotation," Collins said, pointing to outings such as Hefner's start Friday where he allowed two runs in six innings for his fourth quality start in his last six outings. Hefner is 0-5 with a 4.76 ERA.

But Collins also indicated he wouldn't want to send Shaun Marcum (0-5, 6.59) to the bullpen. Marcum, scheduled to start tonight against Atlanta in the finale of a three-game series, hasn't made a relief appearance since 2007 with Toronto.

Dillon Gee didn't help his cause with a rough outing Saturday night that raised his ERA to 6.34.