The Tigers signed the 36-year-old left-hander to a minor league deal two months ago, ultimately assigning him to the Mud Hens roster this spring. In 21 innings spanning 14 appearances, Robertson posted an 0-2 record with a 3.43 ERA, striking out 12 while issuing 13 walks. But left-handers hit .290 against Robertson, who has likely reached the end of his baseball career.
Acquired from the Marlins for pitcher Mark Redman and a minor leaguer before the 2003 season, Robertson made his Tigers' debut in August of the same year. From that point on, he was a full-fledged member of the Tigers' rotation, making 168 starts from 2003 to 2009.
Robertson's best year took place during the Tigers' return to baseball relevance in 2006. He made 32 regular season starts, breaking even at 13-13 with a career low ERA of 3.84 and a career high 208 2/3 innings. He made three post season starts, losing two, including Game 3 of the World Series. Robertson earned his one playoff victory by pitching five shutout innings against the A's a in 5-1 win in Game 1 of the 2006 ALCS.
Coming off career best numbers, Robertson was rewarded by the Tigers in 2007 with a three-year contract extension worth $21 million. But due to injuries and ineffectiveness, Robertson could never come close to replicating 2006.
Falling out of favor after an injury shortened 2009, Robertson was traded to the Marlins in the spring of 2010. Robertson's last appearance in MLB was with the Phillies in September 2010.
Detroit was the fifth minor league organization Robertson has played for since the start of the 2011 season.