"I knew what to expect second time around," he said. "First time, I didn't know anything about it. It helped a little bit that I had been through it once, but it was still amazing, awesome, exciting."
Mathis left Colorado, where the D-backs were playing, late on Saturday night because his wife was admitted into the hospital. He was surprised because they weren't expecting the baby until June 26.
"It was really cool," he said. "It was a little sudden and me getting there was a little stressful, but everything worked out, and everyone is healthy. Everybody got home yesterday."
Mathis rejoined the D-backs in Wednesday's 5-4 loss to the Pirates, going 0-for-3 with a walk. Though he'll be busy, he's still going to be a support system for his wife.
"Listening to her whenever she needs to vent or whatnot," Mathis said. "But, you know, she's been great. She's awesome. She was great with the first one, and I have no doubt she'll be awesome and strong and hold the fort down while I'm gone for this one, too."
In order to make room for Mathis, the D-backs sent down right-hander Braden Shipley. Shipley, a former first-round pick in the 2013 MLB Draft and once thought to be a rotation piece, has pitched three shutout innings in relief at the big league level this season.
In 2017, Shipley made 10 appearances -- three starts -- for the D-backs. He posted a 5.76 ERA.
The club still thinks highly of him, but in a bullpen role.
"Braden did a great job," D-backs manager Torey Lovullo said. "He stepped in in a couple situations. Yesterday, he saved our bullpen. It was the first time I've really seen him throw out of the bullpen after being used in the bullpen in the Minor Leagues. I think this is a good role for him and that we'd continue with that same role -- that was my message to him."
Souza takes a big step
Steven Souza Jr. (strained right pectoral) started a throwing program on Wednesday. He threw for five minutes from 45 feet and, per Lovullo, felt great.
Souza has played in just 14 games this season, batting .163 with an RBI.