"In this game, you never know," Mesa said. "I thought I'd never come back here, but I'm here right now. I've got three good years here, over 100 saves here."
He saved 42 games in 2001 and 45 in 2002, but when that dipped to 24 in 2003, his popularity in Philadelphia waned.
"I have no complaints," Mesa said. "When you are doing bad, expect to get booed. That's what happens. If you're doing good, they are going to cheer you, plain and simple."
Mesa struggled with the Tigers, going 1-1 with a 12.46 ERA. He allowed 19 hits, including three home runs, in 11 2/3 innings. He also spent time on the disabled list with a groin injury.
Mesa appeared in a career-high 79 games last season with the Rockies, where he was 1-5 with a 3.86 ERA.
He said had the Tigers used him more, the results would have been different.
"They didn't give me an opportunity to pitch," Mesa said. "[When they did], I didn't do my job. Every five days [is] not going to do it. They didn't let me pitch. Sometimes you feel strong [when you don't pitch a lot] and you try to throw hard, and the ball stays up.
They decided to go [with someone] else. No question about it, I'm real happy to get out of there."
Mesa said he had "other chances" to go to other clubs.
"But I want to be in the National League, so I can pitch a lot," he said. "In the American League, you don't pitch [as much]."
While Mesa has 320 saves, fifth among active pitchers, manager Charlie Manuel said he would be used primarily in middle relief.
"I'm here to pitch," Mesa said. "Anytime after the sixth, [if] they want to use me, I don't have a problem. I know I'm not going to be the closer here, so I have to pitch when they want me to. I'm ready for it."
"I'll pitch him wherever we need him," Manuel said. "He's always been a guy who has stayed in shape. His experience speaks for itself. Is there a place where he can pitch on our team? Yeah. I think it gives us a more experienced guy."
The Phillies worked out Mesa at their Clearwater, Fla., complex before signing him.
"It was a tryout. I'm a prospect now," the 41-year-old Mesa laughed.
Garcia to DL: Freddy Garcia, who left after 1 2/3 innings on Friday, was placed on the disabled list with a right shoulder strain. He will be examined on Monday in Philadelphia, when the Phillies return for a homestand.
"I think he thought he could go out there and keep pitching," Manuel said. "Even though he was hurting, [he thought] he could still pitch. I think eventually he realized that wasn't good, and that wasn't happening for us."
Manuel is unsure how long Garcia will be out.
"My gut feeling? I don't know," he said. "First of all, until we find out what's wrong with him... That is going to determine how long he is out and how quick he is going to come back."
A sign something was physically wrong with Garcia was his fastball, clocked in the low 90s in 2006, had declined to 83 mph.
"There's a reason for the dropoff of velocity," Manuel said. "There is no way I would pitch Freddy or anybody else that is hurt or play somebody that is hurt. If he's hurting, I don't want to send him out there. If he's hurting himself and his team as he goes out, I don't want to play that guy."
Manuel said he is unsure who will start on Wednesday in Garcia's rotation slot. He said that would probably be announced Monday.
"I think anybody from [Triple-A] Ottawa to [Double-A] Reading who is throwing the ball pretty good has a chance," Manuel said.
Ryan Madson, who made 17 starts last season, has been used strictly in relief this year and is not a consideration.
"I like Madson in the bullpen," Manuel said. "We'll keep him in the bullpen."
One possibility is 22-year-old right-hander Kyle Kendrick, who is 4-7 with a 3.21 ERA with Reading and leads the Eastern League with 81 1/3 innings. On Wednesday, he threw a complete-game victory over Harrisburg, allowing one run on six hits. Kendrick's ERA ranks 10th in the league, while he is 11th with 50 strikeouts.
"Kendrick has improved," Manuel said. "I saw him as a kid, three or four years ago in rookie ball. He pitched for us a little bit in Spring Training. Of course, he's throwing well and he's having success. He's a guy I'm sure we'll definitely talk about."
Jamie Moyer and Royals left-hander Jorge De La Rosa are the pitching probables on Sunday in the finale of this three-game Interleague series. First pitch is slated for 2:10 p.m. ET.