It’s a rough blow to the Royals, as they lose their most consistent starter this season for a few turns. Chen has a 3.59 ERA in 42.2 innings over seven starts.
While he was expected to be a regular in the rotation coming into the season, Mazzaro was left in the minors since the Royals didn’t need a fifth starter for a while to open April. Mazzaro got off to a rough start in Omaha, walking seven over 2.1 innings in his first start. He’s settled down since, walking just six over his next 23 innings. His ERA in Triple A sits at 4.97 and he’s struck out 27 over 25.1 innings, including 10 on April 30.
Danny Duffy, Everett Teaford or even Mike Montgomery were other candidates for promotion, but without knowing the severity of Chen’s injury, or if he simply needs some time off, they’d be more likely call-ups when the Royals can see them all season.
For a solid scouting report on Mazzaro, check out Gage’s profile from November after the Royals had acquired him (along with Justin Marks) for David DeJesus. He also broke down Mazzaro’s final start of the 2010 season for Oakland, inning by inning.