Catcher Dan Wilson took a swing during morning batting practice and pulled the oblique muscle in his left side, a painful injury that doesn't heal quickly.
Wilson missed a month during the 2000 season with the same injury.
The severity this time won't be known until Dr. Larry Pedegana, the Mariners' medical director, examines Wilson on Sunday.
With less than three weeks remaining before the Mariners leave for their season-opening series in Japan, Wilson could miss a significant amount of the exhibition schedule.
"Danny is a big guy for us and it's a concern," said manager Bob Melvin, a former catcher who has suffered the same injury himself. "These things tend to take a little while and if you do re-injure it, it's not a good thing.
"We need to take our time with him and make sure he's healthy."
Wilson went through one round of batting practice with no problems, then took a swing during his second round in the cage and felt the strain.
"It doesn't feel too good right now, but hopefully it's not bad," Wilson said.
If Wilson is out for an extended period, Ben Davis will get most of the starts with 38-year-old Pat Borders as his backup.
Davis battled an oblique strain, on his right side, during spring training last year and it lingered well into the season.
"It's a terrible injury," Davis said. "Next to a hamstring, it's one of the worst injuries you can have. It prohibits you from doing anything. You don't realize you use all those muscles on a daily basis. If you sneeze, it kills you. If you cough, take a deep breath, anything, you feel it."
Davis eased up on his weight-lifting regimen in the offseason in an effort to avoid such strains.
"I don't know why there's been so many of these in the last couple of years," he said. "I think everybody has gotten so worried about their midsection, keeping it tight and strong.
"I think the muscles are getting so tight that they don't have anywhere to go, and they just rip. Exerting all that effort, the muscles just can't hold it."
Mariners glance
- Friday: Angels 6, Mariners 4; Padres 16, Mariners 4.
- Today: Seattle vs. San Diego, noon in Peoria, Ariz. (1030-AM).
- On the Web: Find links to the Peoria Sports Complex, spring training ticket sales, the M's 2003 schedule and more in the Mariners 2003 section at www.theolympian.com.
The Olympian Online
On the Web
• Peoria Sports Complex Spring Training 2003