Mendoza has not allowed a run in seven innings, giving up just one hit with no walks and four strikeouts, and manager Ned Yost has certainly noticed.
"He has gone from totally being off my radar to being right in the middle of it. He came to camp and has changed his delivery. He's more downhill, there's nothing flat about his pitches anymore. He's been very impressive, a very bright spot for me," Yost said.
"Last year, Bruce Chen was that guy -- off the radar, nobody paying any attention to him and, all of a sudden, boom! And Mendoza has been that guy for me this year."
Mendoza, 27, from Mexico City, appeared in four games for the Royals last season and gave up 10 runs in four innings. For Triple-A Omaha, he was 10-9 with a 4.10 ERA in 24 games, primarily as a starter.
"This is a different Mendoza from what we saw last year," Yost said.