"It's just a matter of when, is it the fourth game or the fifth?" D-backs manager Kirk Gibson said. "But unless he has a severe setback, I expect him to be ready."
Arroyo is scheduled to start his first Major League preseason game since Feb. 27 on Saturday at Chase Field against the Cubs.
As for McCarthy, the honor to start the D-backs' home opener is not wasted on him. Even though the club already began its season in Australia, he anticipates the game to feel just like Opening Day.
"It's a cool opportunity, for the fans it's their first chance to get out and see you guys again," McCarthy said. "There's always a lot of atmosphere there, it's kind of the closest you get to a playoff atmosphere in the regular season until the season starts drawing to an end. It'll be fun."
McCarthy, who previously made an Opening Day start for Oakland back in 2012, capped off an impressive spring Wednesday with another strong outing, this time tossing six innings and surrendering three runs on six hits while striking out six. Overall in 20 Cactus League innings, McCarthy posted a 2.70 ERA with 12 strikeouts against just three walks.
"I executed a lot this spring," he said. "I threw most of my pitches where I wanted to, I threw with conviction and was able to accomplish what I wanted to while I was here. Those are all good things, but how they'll translate into regular season results, we'll find out, but I feel like I'm in a good place."
Added D-backs bench coach Alan Trammell, "He looks like he's on a mission. He's kept them off balance and that's what makes him effective. That's what we need to see from him this year."
Steve Gilbert is a reporter for MLB.com. Read his blog, Inside the D-backs, and follow him on Twitter @SteveGilbertMLB. Tyler Emerick is a reporter for MLB.com. This story was not subject to the approval of Major League Baseball or its clubs.