Garland, who in January signed a one-year deal worth $4.7 million which includes a $600,000 buyout for 2011, will face Dan Haren and the Arizona Diamondbacks in Phoenix on April 5.
Last season, Garland went a combined 11-13 with a 4.01 ERA for the Diamondbacks and the Los Angeles Dodgers.
Black also announced that Chris Young would be the Padres' starter in the season's second game, and Kevin Correia would pitch the series finale against Arizona.
"It's a big honor, especially being my first year with the team," Garland said. "(Chris Young) was an All-Star, Kevin (Correia) had a great year last year for them -- they are definitely deserving."
Black said any of his top three pitchers would have been strong choices to start the season. Young, who is healthy after undergoing arthroscopic shoulder surgery last August, is considered one of the team's leaders, while Correia posted career highs in wins (12), innings (198) and games started (33) in 2009.
"We feel pretty good about those three," Black said. "They're comfortable pitching at the top. They've all thrown the ball well this spring."
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Garland missed one start with what he's calling a "hiccup" after a knot developed in his throwing shoulder. But the right-hander, who has averaged 32 starts and 205 1-3 innings over the past eight seasons, looked sharp in a start against the Milwaukee Brewers on Friday. He said he was especially excited to hear the news from Black.
"He said, `I like the way you go about your business ... and I want people to follow your lead,"' Garland said. "It was sort of a pat on the back for him to have that respect for me. He's been good to me ever since he was the pitching coach in Anaheim. Coming from a guy who was a pitcher himself, and a pretty good one, that feels good."
In other news, the Padres are being cautious with left-hander reliever Joe Thatcher's shoulder. Thatcher, who last pitched on March 19, had a cortisone shot on Saturday and is expected to miss several days. Black said there is a possibility that Thatcher, who was 1-0 with a 2.80 ERA in 52 games in 2009, could miss the start of the season.