"He's doing a great job for us," Gibson said. "He throws sliders, has a cutter and has a good mentality [for late-inning situations]."
One area in which Harris can improve is his walk rate. He's issuing free passes at a clip of 2.92 per nine innings and has struggled with command of his offspeed pitches at times.
"There's been a lot of three-ball counts," Gibson said. "We'd like to see him cut down on his pitches."
Gibson pointed to a moment in Friday's game when Harris threw consecutive breaking balls a few feet short of home plate.
"It was pretty obvious the next pitch would be a heater," Gibson said. It was, and Jeff Francoeur -- a noted fastball hitter -- doubled to lead off the inning.
Harris induced three consecutive groundouts to escape the eighth inning.
"We're moving him into higher situations [recently]," Gibson said. "He's done a good job."
Andrew Owens is an associate reporter for MLB.com. Follow him on Twitter @OwensAndrew. This story was not subject to the approval of Major League Baseball or its clubs.