The former Tigers left-hander reinvented himself during the offseason, opting to change his arm angle to slightly below three-quarters, making him more of a threat to get left-handed hitters out late in ballgames.
Robertson, whose career was derailed by elbow problems, has impressed this spring with three shutout innings, during which he allowed two hits.
"I've had some elbow issues in the past, and I felt like in the last several years my ball has flattened out quite a bit," the 33-year-old Robertson said. "Now, it's just a different look. But with the arm slot, the movement in the zone is big."
He feels the new arm slot provides him two things that had been lacking during the past two seasons -- seasons he spent in the farm systems of the Mariners, Cubs and Blue Jays. First, it creates an element of deception to his delivery. Second, it adds movement to his pitches -- more sink on his fastball and more bite on his breaking ball.
Robertson's best season came in 2006, when he posted a 3.84 ERA and a 13-13 record, earning the Tigers' Game 1 start in the first two rounds of the playoffs. After that, he fell off considerably as a starter, forcing him to reinvent himself. The Rangers sent a scout to watch him during the offseason and opted to take a chance on him as a non-roster invitee.
The Rangers' No. 5 starter role is up for grabs, but Robertson said he's focused on his job as a reliever, and the Rangers haven't approached him with any suggestions otherwise. He says that's probably for the best.
"I came in here with a plan of what I was trying to be," Robertson said. "Obviously there were needs here in the bullpen in Texas. With that match, they brought me in."
As a starter, Robertson's numbers were considerably better against left-handed hitters, but manager Ron Washington said he wouldn't see a problem using Robertson against righties, too. As for Robertson's new, crafty approach to the mound, Washington had nothing but praise.
"He's out here competing with a changed style, and he's making it work," Washington said. "... We know he knows how to pitch. He knows how to win at the Major League level, and he's not afraid to use what he has right now."