"It's something I thought would be really cool for it to happen, and it's coming to fruition," said Hudson, who spent 1999-2004 with the A's and migrated to Atlanta before joining the Giants prior to the 2014 season. Zito rose to the Majors with the A's in 2000, joined the Giants as a free agent in 2007 and sat out last season before returning this year to pitch at the Triple-A level with Oakland.
"I hope the fans appreciate it," Hudson said.
Sunday, Hudson and Zito will be joined by the the third member of that vaunted A's rotation, left-hander Mark Mulder, as all of them will throw ceremonial first pitches.
From 2000-04, the years they pitched together in Oakland, Hudson posted an 81-37 record, Mulder was 81-50 and Zito went 72-40.
"It's something all three of us will look back on. That's a special time, for sure," said Hudson, who called that period "some of the funnest, best years for all three of us."
Giants manager Bruce Bochy is looking forward to seeing Zito perform.
"I really admire what he has done, playing for the love of it," Bochy said.
• Buster Posey was scratched from the Giants' starting lineup Tuesday with tightness in his back and hip. Posey, who entered the game with a .327 batting average, third in the National League, was available to pinch-hit and predicted he will start Wednesday.
"I just want to get my legs under me and finish up as strong as possible," said Posey, who was replaced at first base by Ehire Adrianza in his initial professional appearance at first base.
• Outfielder Juan Perez is likely done for the season, another victim of an oblique injury. The discomfort is enough to dissuade Perez from playing winter ball after six years in a row of performing for Aguilas Cibaenas in the Dominican League.
"I have to give my body a rest," said Perez, who batted .282 in 22 games for the Giants as well as .265 in 83 games for Triple-A Sacramento.
Right fielder Hunter Pence and shortstop Brandon Crawford are others who have contended with oblique ailments.