Koehler had a career night on Saturday, even though he came out on the losing end of the Marlins' 1-0 decision to the D-backs.
One pitch -- his first of the night -- haunted Koehler, as Gerardo Parra belted Koehler's 94-mph fastball over the wall in right field. Besides that, it was a promising second start of the season for the New Rochelle, N.Y., native.
"I'm happy with the command," Miami manager Mike Redmond said. "I think we were always, maybe in Spring Training, a little bit worried about his command and how he'd command the strike zone.
"But he's come up and just done a nice job. I think what I'm most impressed with is how he's been able to use that curveball to kind of get his fastball down in the zone and be a nice secondary pitch for him. As he goes through a lineup for the second and third time, he's got that as a weapon, and he's been able to command it, and that's the key. He's been able to do that the last couple of days. It was fun watching him."
Koehler struck out seven in six innings.
Arizona manager Kirk Gibson was impressed.
"He's got a good arm, very lively arm, and he had good velocity," Gibson said.
Since joining the rotation, Koehler has a 2.45 ERA with eight strikeouts in 11 innings.
He walked two and had a number of deep counts, which raised his pitch count to 94. Being more economical with his pitches remains a point of focus.
"I hope next time I can limit the pitch count a little more, and eliminate some of those three-ball counts, and try to get into the seventh and eighth innings," Koehler said.
Joe Frisaro is a reporter for MLB.com. He writes a blog, called The Fish Pond. Follow him on Twitter