Rasner began his major league career with the Washington Nationals, pitching in a few games late in the 2005 season. He was claimed off waivers by the New York Yankees in the 2005 off-season.
Rasner recorded his first major league win on September 3, 2006, in a game he started for the Yankees against the Minnesota Twins. Rasner went 6 innings, allowing 4 hits, 1 earned run, 2 strikeouts and no walks in a 10-1 victory.
On May 19, 2007, in a start against the New York Mets, Rasner was struck on the right hand by a ball hit by Endy Chavez, a former teammate with the Nationals. He fractured his right index finger and did not pitch in the major leagues again that season, though he pitched at several levels of the minor leagues on rehab assignments.
Rasner was not offered a new contract by the Yankees and became a free agent on December 12, 2007, but was re-signed a couple of days later to a minor league deal.
On May 4, 2008, Rasner was recalled by the Yankees, and made his season debut against the Seattle Mariners. Rasner worked 6 innings, allowing only 2 runs and stayed in the Yankee rotation until September, when he was replaced by Alfredo Aceves. It was during this impressive four month stretch that he earned the cult nickname “The Showstopper” by Yankees fans and the New York press.
On November 15, 2008, the Yankees sold Rasner to the Tohoku Rakuten Golden Eagles for $1 million. Rasner signed a two-year deal with the Golden Eagles.