But thus far in 2012, the two 30-somethings have been solid for their respective clubs, and they'll look to continue that Wednesday.
In the second game of a three-game set, Zambrano is looking for his first win as a Marlin and Zito aims to continue his best start in quite a while.
The lefty Zito is 1-0 with a 1.67 ERA this season. In four starts, the 2002 Cy Young winner has allowed just five earned runs over 27 innings.
He'll be looking to prolong a funk for the Marlins' hitters that has stretched throughout this season. They are just 2-8 in their last 10 games, but starting pitching has rarely been the issue.
"I don't think we've seen any easy pitching yet," Miami manager Ozzie Guillen said. "But everybody pitching against us right now looks like they're in the race for the Cy Young Award."
Zambrano is 5-1 with a 2.55 ERA lifetime against the Giants. On Sept. 25, 2009, at AT&T Park, he had a two-hit shutout. In his five career starts there, Giants hitters are 23-for-121 (.190) off Zambrano.
He had to battle his last time out to earn a quality start, allowing 10 hits but just three runs in six innings. That game brought his ERA to 3.24 this season.
Guillen hasn't been pleased with his hitters squandering efforts like Zambrano's, but the Marlins did hang on Tuesday for a 2-1 victory.
"When you waste your starting pitching like that, it hurts," Guillen said before Tuesday's game. "You're wasting guys' quality starts, and you don't win games. That's the way it is. But on the other hand, it's something that is very positive. It gives you an opportunity to win every game."
Marlins: Bell has Guillen's support
Closer Heath Bell blew three of his five save chances before a clean 1-2-3 inning Tuesday night to pick up his third save.
Even before the game, Guillen remained firmly in support of Bell, whom he reiterated is not in danger of losing his closer role.
"I think he threw the ball a little bit better [Monday], even though the result is not what we like," Guillen said. "He has to make an adjustment. He's our closer. We are a better ballclub when Heath Bell is in the closer spot."
All 22 of Emilio Bonifacio's hits this season have been singles. That's the longest stretch of singles to start the season in club history. Chris Coghlan had 21 straight in 2010.
The Marlins have been on the road quite a bit this season, as they lead baseball with 21 road games through the first five weeks.
Giants: Affeldt to DL
Reliever Jeremy Affeldt sprained his right knee while hoisting his son, Walker, for an embrace Saturday. Following an MRI and a few examinations, the Giants placed the lefty on the disabled list.
"When he jumped, I kind of caught him weird and my knee kind of shifted in a little bit and I felt some pressure on the knee," said Affeldt, who is 0-1 with a 4.09 ERA in 10 appearances this season.
The Giants purchased the contract of left-hander Travis Blackley from Triple-A Fresno to replace Affeldt. Fresno outfielder Tyler Graham was designated for assignment to clear a 40-man roster spot for Blackley.
Angel Pagan extended his hitting streak to 15 games Tuesday, the longest active streak in the Majors.
After a 1-for-9 effort Tuesday, the Giants are now hitting just .193 with runners in scoring position.
Hitters on the current Marlins roster have struggled against Zito in the past, combining for just a .165 batting average and a .232 on-base percentage. Of the six Fish with more than three at-bats against Zito, none are hitting above .300.
The Marlins have struggled in San Francisco, posting just a 27-48 lifetime record.