He added that he believes Broxton's struggles in the role earlier this year were due to the right-elbow injury that presently has the right-hander on the 15-day disabled list.
Broxton began a minor league rehabilitation assignment at Triple-A Albuquerque Tuesday night, when he started against Oklahoma City and gave up a run on one hit with two strikeouts in one inning. He is scheduled for at least one more appearance with the Isotopes Thursday, and he probably won't be activated until next week at the earliest.
"The ball was coming out pretty good," Mattingly said of the reports he received. "I think he was at 94 to 97 (mph). It was encouraging because the velocity was there."
Broxton lost his job as the Dodgers' closer last summer just a month after logging the save in the All-Star Game, then appeared to lose it again earlier this season before going on the DL May 6.
His ERA at the time was 5.68 and opposing batters were hitting .283 against him, all at a time when his fastball routinely was topping out in the low 90s.
"Usually, when a guy is normally 98 to 99 (mph) and a year later he's at 91, something is wrong," Mattingly said. "That usually doesn't lie. You can say it's mechanical this or mechanical that, but at some point, that is a huge difference. We felt like seeing it jump in his first outing back was a sign something was going on."
Mattingly said when Broxton does return, he won't be used as the closer initially.
"I think we'll try to get him into some games first," Mattingly said. "(But) I think it would be best (for him to close) if he is throwing the ball the way he is capable of. Again, right now, we have to get him in there and see what it looks like."
Tony Jackson covers the Dodgers for ESPNLosAngeles.com.