The Yankees have optioned Adam Warren, who was shelled in his MLB debut Friday night, to make room for D.J. Mitchell on the roster.

Mitchell's season has had it's share of ups and downs.

"Early in the year I started off really well, then kind of hit a bump in the road this month," said Mitchell, who was called up from Triple-A Scranton/Wilkes-Barre and arrived at Yankee Stadium on Saturday morning.

"But in my last start, I kind of figured some things out, started getting back on track and hopefully I can keep it going."

Mitchell posted a 7.16 ERA in five June starts for Scranton, but, as he noted, he went seven innings and gave up a run on five hits, earning the win on Tuesday. Overall, he's 5-4 with a 5.36 ERA in 14 starts.

Mitchell, 25, said the reason for his recent struggles was mechanical, but he believes he has fixed it in subsequent bullpen sessions. The right-hander is going to be a long reliever for the Yankees.

"I don't think that's a big deal," Mitchell said of the transition from the rotation into the bullpen.

Mitchell, who nearly made the Yankees out of spring training, has made two May relief appearances for the big club in 2012, giving up one run on four hits in 2 2/3 innings.

The Yankees selected Mitchell in the 10th round of the 2008 draft.