The AL MVP hit his second home run of the game in the 10th inning, giving the Los Angeles Angels a 2-1 victory Saturday. Guerrero tied the score with a shot in the eighth against Jim Mecir, spoiling Willis' bid to become the first 12-game winner in the major leagues.
"I don't think it was a matter of Dontrelle coming out of the game, because we had connected so well against him," Guerrero said through a translator. "But we were ready for somebody new."
Willis, who threw 107 pitches, was pulled by Marlins manager Jack McKeon with a 1-0 lead after scattering 10 hits through seven scoreless innings and stranding five runners in scoring position.
"I don't care about my giving up that number of hits. I just wanted to keep them from scoring. That's the name of the game," Willis said. "I made some big pitches and had some great defensive plays behind me. I was able to make some key pitches against Guerrero, but he's the MVP and he showed why today."
Guerrero greeted Mecir -- the loser in Friday night's series opener -- with a homer to start the eighth. Two innings later, he hit a leadoff drive off Todd Jones (1-2) into the left-field bullpen on a 3-2 pitch.
"He hit a hanging curveball that was nowhere near where I wanted to throw it," Jones said. "It was a terrible pitch. We spent the majority of the time in our pitchers' meeting on him and how he's not supposed to beat us -- and he got us twice today.
"I know he's aggressive. He'll swing if you get it close, and he'll hit it out if he can reach it. So it's one of those tough lines to walk. He's a special player."
It was Guerrero's 10th homer this season and the 21st of his career against the Marlins. The five-time All-Star has eight game-ending homers in his career, the other seven with the Montreal Expos.
McKeon, the 2003 NL manager of the year, defended his decision to go to the bullpen.
"We didn't want to take him out. But if we let him go another inning, he was going to be up in the 120s," McKeon said. "I didn't want to overextend him because we're going to need him every five days, and we're going to have to count on him to be the horse the rest of the way. But you've got no margin for error no matter who's out there."
Francisco Rodriguez (2-1) pitched two perfect innings for the win.
The Angels had a great opportunity to win in the ninth against lefty Valerio De Los Santos, but Darin Erstad hit a grounder with the infield in to shortstop Alex Gonzalez, who started an inning-ending 6-2/3 double play. It was the first double-play grounder in 269 at-bats this season for Erstad, who along with Kevin Mench and Jim Edmonds were the only players who had not grounded into one.
In a matchup of former World Series rookie pitchers, Angels right-hander John Lackey matched zeros with Willis through five innings before the Marlins broke through.
Luis Castillo, 4-for-6 on Friday night, singled his first three times up against Lackey - including a bunt hit leading off the sixth. He went to second on a wild pitch, was held at third on Miguel Cabrera's single to right and scored on a single by Carlos Delgado that extended his hitting streak to 13 games.
But the Marlins didn't get another hit.
Lackey escaped further damage later in the inning by retiring Juan Encarnacion with the bases loaded. Lackey allowed a run and six hits in 6 2/3 innings. He struck out seven, walked three and threw three wild pitches.
Lackey's previous two starts were against Cy Young winners Pedro Martinez and John Smoltz. And it wasn't any easier this time against Willis -- the NL's leading candidate to start the All-Star game. But the Angels won all three games, with Lackey getting a no-decision each time.
"I'm more concerned about the lineup than the pitcher," Lackey said. "But what do you expect -- I mean, going against three guys that are big-time, front-line starters? But for the team to win, I must have done something right."
- Willis and Lackey both won World Series rings as rookies. Willis made three relief appearances in 2003 against the Yankees. Lackey started Games 4 and 7 in 2002 against San Francisco and pitched in relief in Game 2.
- Angels RHP Paul Byrd, Sunday's scheduled starter, was pushed back to Monday against Texas because of tightness in his triceps. Ervin Santana, filling in for the injured Kelvim Escobar, will move up a day in the rotation and start Sunday on his normal rest.
- Erstad extended his career-best hitting streak to 18 games with an opposite-field single in the third. His 196 interleague hits are the most since interleague play began in 1997.
- Willis has not allowed a home run in 69 1/3 innings since April 23, when Cincinnati's Felipe Lopez hit a two-run shot in the Marlins' 4-2 victory.