The A's open their season in Japan on March 28. Bartolo Colon will start the second game the following day.
"He was a natural pick after last year and with the pitchers we ended up trading away," Melvin said of McCarthy. "He's been focused this spring knowing he has to get ready a little earlier. He looks like he's in midseason form."
McCarthy had career highs in wins, starts, complete games, innings pitched and strikeouts last season. He was 9-9 with five complete games in 25 starts, and had 123 strikeouts in 170 2/3 innings.
McCarthy also recorded a 4.92 to 1 strikeout-to-walk ratio, the highest by an A's pitcher since 1901. He walked 25 batters.
"He's so precise, so focused, that sometimes he doesn't think about throwing a ball for effect," Melvin said. "He doesn't change the eye level. The fewer guys you put on base, the fewer opportunities they have to score."
McCarthy, who signed with the A's as a free agent after spending 2010 in the minors, did not hit a batter last season.
"I know what it takes to get ready for a season," McCarthy said. "If you are mentally ready, however your work is the right path. I feel comfortable and am what where I want to be."
McCarthy's wife, Amanda, also expressed her feelings in a tweet: "Last year fighting for a spot this year opening day guy. So unbelievably proud of my husband! Ready to get my cheerleader on!"
Colon, signed as a free agent in January, is a 14-year veteran with 161 career wins.
"He's a calm guy, a calm thinker and just goes about his business," Melvin said. "His mechanics, to me, really stand out. He may not be one of the most talkative guys but when he gets on the mound he knows what works for him. He can read hitters well."
A's catcher Kurt Suzuki on losing third baseman Scott Sizemore (torn ACL in left knee) for the season: "There's nothing you can say to make him feel better. You just try to be a good friend and a good teammate. He was so dedicated and so excited for the season, and such a freak accident, it sucks." ... RHP Brad Peacock felt some back stiffness Monday and was given a day off. He'll throw to hitters one more time before being used in a game. ... The A's scheduled a four-inning scrimmage for Thursday at Phoenix Muni.