SAN DIEGO (AP) _ The first-place San Diego Padres have played through stretches when star players Tony Gwynn, Ken Caminiti and Rickey Henderson sat out due to injuries.

But none missed the 6-8 weeks that smooth-fielding first baseman Wally Joyner will because of a fractured left thumb.

``It's not good,'' said Caminiti, who recently missed 15 of 17 starts with a groin injury. ``He's a key part of our lineup, a key part of our defense.''

The left-handed Joyner, hitting .321 with five homers and 33 RBIs, broke the bone at the base of his thumb while sliding into second base in the fourth inning of Sunday's loss at Philadelphia. His thumb was placed in a cast then, and he was examined Monday at Scripps Medical Clinic by team doctor Jan Fronek and hand specialist Dr. Merlin Hamer.

Results of an MRI showed no ligament damage.

Fronek said Joyner will be in a cast for four weeks, and will then require 2-4 weeks of rehabilitation. Once Joyner's back, he'll still have some stiffness, Fronek said.

``There's still a fair amount of work. That area is a little more sensitive,'' Fronek said.

Joyner, adept at scooping throws out of the dirt, was placed on the 15-day disabled list. The Padres recalled left-handed reliever Ron Villone from Triple-A Las Vegas.

``He's as smooth as they come,'' Caminiti said of Joyner. ``It almost looks like he expects a bad hop, and he's ready for it every time. I hope we can get by. We've got guys who can fill his spot, but they're not Wally Joyner.''

Said pitcher Bob Tewksbury: ``I'm sad because of what he does for us as a team. Individually, I'm just really sad for him because he's having a lot of fun. He's in a new league and he's playing well. Every day, he's happy.''

Archi Cianfrocco, who earlier filled in at third base for Caminiti and in right field for Gwynn, started for Joyner on Monday night. Manager Bruce Bochy said Marc Newfield will play at first Tuesday night, and the Padres will also use left-handed hitting Scott Livingstone there. However, Bochy said Livingstone has a sore lower back and may need a few days of rest.

``When you lose one of your starters it's always a big blow,'' Bochy said. ``I think we're fortunate to have some depth on the bench. We can piece this together.''

First base ``is my best position,'' Cianfrocco said. ``That's where I feel most comfortable.''

``It's definitely a big blow,'' Cianfrocco said. ``It seems like we're always missing a guy. Wally's been a steady player for us.''

Joyner was trying to break up a double play when he caught the bag with enough force to break his thumb. The training staff originally thought he had sprained it, and Joyner remained in the game, but was taken out an inning later due to the swelling.

The Padres acquired Joyner from Kansas City on Dec. 21 for second baseman Bip Roberts and pitcher Bryan Wolff.

Villone, 26, has spent the entire season with Las Vegas, appearing in a team-leading 23 games. He was 2-1 with a 1.64 ERA and three saves.

The Padres acquired Villone along with Newfield from Seattle last July 31 for Andy Benes and Greg Keagle.