The right-hander picked up his fifth save of the season on Wednesday, when Miami beat the Braves, 4-2, at Turner Field.
Asked if Cishek can be a quality closer in the big leagues, Guillen said: "Yes, he throws strikes."
A rangy 6-foot-5, 200-pounder, Cishek has a deceptive sidearm delivery. Unlike many who drop their arm angle, the Falmouth, Mass., native has pretty good velocity. He throws in the 92-93 mph range, which is plenty of velocity. Normally, right-handed sidearm pitchers don't touch as high as 90 mph.
Cishek has struck out 42 in 44 1/4 innings, while walking 20. So he's showing command and control.
He's been especially tough on right-handed hitters, who are batting .163 against him. Left-handed batters are more effective at .299.
With more chances, Guillen feels Cishek will improve against lefties.
"I think you will see overall that he will start throwing better against lefties," the manager said. "He's throwing a little better to righties than to lefties. The more maturity he gets, and his breaking ball is thrown for a strike. And he uses his changeup. I don't see why not."
Effective closers, Guillen said, have at least one strikeout pitch.
"It could be a changeup, slider or a fastball," the manager said. "If you've got one pitch to strike a guy out, and you have to throw strikes, you will be fine."