Souza had been out of action since injuring his right pectoral muscle while diving for a ball on March 21. He experienced a slight setback in his rehab process when he felt some soreness in the muscle while ramping up his throwing program in early April.
Even when Souza stopped throwing for a while, though, he continued to hit, getting close to 50 at-bats in extended spring games.
"I'm excited," Souza said before Thursday's game vs. the Dodgers. "It's been a long process. Everything feels 100 percent. Throwing is completely back to normal. We passed all the tests. Offensively, I've been ready to go for a while now."
Souza joins a team that entered the day with the National League's best record at 21-9.
"Just feeling helpless, but trying to stay locked in and watch pitchers and support the team in any way I can," Souza said. "It's been fun watching, and it's going to be even more fun playing."
While Souza will try to be smart about diving for balls and unleashing his throwing arm, there's only so much he can do given the way he plays the game.
"I'm going to do my best, but I think as we've seen, I like to play all out," Souza said. "I'm going to do my best to be smart in some situations, but if somebody tries to test it going first to third …"
A long road back Kris Medlen will be added to the 40-man roster and called up from Triple-A Reno to start Friday's game against the Astros.
Medlen has not appeared in a Major League game since May 10, 2016, when he was with the Royals, and he has battled back from two Tommy John surgeries. The first surgery was in 2010, and the second came in '14.
Medlen's former teammate with the Braves, Jonny Venters, recently returned to a big league mound after undergoing three Tommy John surgeries.
After pitching at three levels of the Braves' system last year, Medlen signed a Minor League deal that included a Spring Training invitation with the D-backs.
Medlen had been scheduled to start for Reno on Monday, but he was scratched and told that he would be headed to the big leagues to take the place of injured starter Robbie Ray.
"It's everything," Medlen said of getting the callup. "I'm no Jonny Venters, but I've been through a little bit in terms of injury, and this is something at one point a couple of years ago when I was going to retire, something that I honestly wanted to happen, but thought it would never happen. I just have a ton of gratitude for this organization giving me a shot."