"I've been feeling pretty good," Gutierrez said on Saturday, a day after throwing his second bullpen session since being placed on the DL on May 25 with a shoulder injury.
"I felt really strong," he said.
Gutierrez is scheduled to throw another bullpen on Monday, and expects a decision on his return to be made next Thursday.
In the three weeks since being placed on the DL, Gutierrez has also shed 13 pounds.
"How can you not notice?" D-backs manager Kirk Gibson asked. "He's much smaller. He's worked hard, he's in good shape and threw the ball pretty decently yesterday."
Gibson said they're going to increase the intensity during his next bullpen before letting him face live hitters.
"I've been working really hard," Gutierrez said. "We've been doing a lot of things in the weight room, working hard there and doing a lot of conditioning at Salt River [Field]."