Harrison was an 18-game winner and the Rangers' Pitcher of the Year in 2012. But he has been limited to six starts over the past two seasons while dealing with serious back issues. He has undergone three back operations, the last one being spinal fusion surgery June 3, 2014.
There is no history of a pitcher coming back from that type of surgery, but Harrison is on the verge of setting a new medical precedent.
"I feel good physically and mechanically," Harrison said. "I just need to get out there. I have learned to pitch with less stuff, but I'm confident in myself that I can command the strike zone, be aggressive and get people out. The movement is still there, my breaking pitches are still there, my changeup is still there. Just less velocity, but that will come back in time.
"There will be a lot more adrenaline and a lot more emotion, but it's hard to say exactly what it will feel like. It's almost like starting over; the last two years have been rough."
Harrison made six starts on medical rehab assignment and was 1-3 with a 6.23 ERA. But manager Jeff Banister watched him throw two bullpen sessions on the previous road trip and liked what he saw.
"The ball was coming out of his hand cleanly," Banister said. "He had good velocity and his breaking ball was crisp. His fastball had good sink and running life to it. With Major League rehabbing players, there is something to be said for what they are used to and the arena they play in, the Major League experience.
"They don't always get that feeling on a rehab stint. It comes down to the medical evaluation, how they respond coming out of the game, their strength, more than the actual performance. You would like for the guy to have the same adrenaline, intensity and focus, but it's not always the case."
• Outfielder Delino DeShields, on the disabled list with a strained left hamstring, is hitting .350 (7-for-20) in five games on medical rehabilitation assignment at Triple-A Round Rock. Said Banister, "He has responded well. Each day he is feeling progress. I would think there is a chance to be back before the All-Star break, but it's a hamstring and he is a speed guy. We don't want to rush it."
• Derek Holland threw a bullpen session Friday, the first time he has been off the mound since starting the home opener April 10. He is on the disabled list with a strained muscle in his left shoulder and is not expected back until August.
• Martin Perez, in the final stages of recovering from Tommy John elbow reconstruction, allowed two runs in four innings in a start for Round Rock on Thursday. He threw 73 pitches in his fourth rehab start. Perez is scheduled to pitch two more times on rehab before the Rangers have to make a decision on him.