The Friars will work out on Sunday at PETCO Park in preparation for Monday afternoon's opener against the Giants, matching Jake Peavy against Jason Schmidt.
"He's pretty sore today," head athletic trainer Todd Hutcheson said of Cameron, who was wrapping up a superb spring when he suffered the injury in batting practice Friday night. He'll have an MRI in a few days to assess the bleeding in the tissue.
"Walking around, he's fine. If he has to make any quick movements, it hurts him. If he tries to come back too early and re-injures it, it could take a couple of months. In three to four weeks, he should be in pretty good shape. Obviously, we'll try to minimize the time he misses, but at the same time we need to be careful with it."
While the contract of Sweeney was purchased from Triple-A Portland, pitcher Eric Junge, third baseman Justin Leone and outfielder Eric Valent were reassigned and are expected to play for the Pacific Coast League Beavers.
The club detoured from its plan of carrying 11 pitchers to go with 12. Cassidy and Sweeney join a middle relief corps alongside starters Woody Williams and Chan Ho Park, one of whom will rejoin the rotation in two weeks.
Alan Embree is the lone southpaw in the bullpen, with Clay Hensley and Scott Linebrink the principal setup men for closer Trevor Hoffman.
In Cameron's absence, for at least two weeks, Dave Roberts moves back to center from left. Terrmel Sledge is expected to open in left field and play against right-handers, with Eric Young and Johnson options. Brian Giles also can shift to center, with Johnson or Sledge in right.
"We're covered in the outfield," manager Bruce Bochy said, acknowledging that Cameron's premium defense, speed and power and dynamic presence will be missed.
Embree, Sweeney and Cassidy prevailed amid a collection of candidates for spots in the bullpen.
Making his return to San Diego, where he flourished in 2002, Embree had a 5.87 ERA in eight appearances, walking two and striking out five in 7 2/3 innings.
In seven spring appearances covering 10 innings, Sweeney, 31, authored a 3.60 ERA, striking out eight while walking four and giving up 15 hits.
The Yonkers, N.Y., native has thrown 1,064 1/3 Minor League innings with a 71-47 record and 3.97 ERA. He owns one Major League victory -- at the expense of Randy Johnson in 2004 -- with a 4.12 ERA in 12 games.
Cassidy, 30, had a 4.32 ERA in seven spring outings, walking none and striking out seven in 8 1/3 innings. Another New Yorker, from Syracuse, he was 1-1 with a 6.57 ERA in 10 games with the Padres last season and has a 2-5 career record with a 6.15 ERA in 69 games.
"They're strike throwers who are not going to beat themselves," Bochy said of Sweeney and Cassidy. "And Eric [Junge] is the same way. It was a tough call. All of them pitched well enough to be on the club."
Leone and Valent also had productive springs in making it to the final cut.
Junge, 29, went 3-0 with solid work in seven of his eight appearances. Leone, 29, tripled and doubled Saturday against the Cubs, giving him eight extra-base hits in 44 spring at-bats. He had three homers and 11 RBIs.
Valent, who turns 29 on Tuesday, tasted Major League success with the Mets in 2004 (13 homers in 270 at-bats) and could be back. A left-handed hitter capable of playing all three outfield positions and first, he's the all-time Pacific-10 Conference home run king with 69, outdistancing the likes of Mark McGwire and former UCLA teammate Troy Glaus.
Springing to prominence:
General manager Kevin Towers pinpointed the performances of second baseman Josh Barfield and pitcher Dewon Brazelton in forging significant roles as individual spring highlights.
Barfield, who excelled defensively, banged out two more hits Saturday, finishing the spring with a .433 average. After a shaky start in severe winds, Brazelton settled down to get nine straight outs in a five-inning stint that he felt prepared him well for his scheduled start Friday night against Colorado at PETCO Park.
"It was a real good thing, everything that happened today," Brazelton said. "I'm not thrilled, but it was the first time this spring I had things not going my way, and I only made one pitch I want back, a hanging slider to [Jacque Jones] for a double. I felt really good and threw a lot of quality pitches. I could see myself going to the seventh, eighth, ninth inning."
Towers feels the club's offense and defense will be improved, reserving judgment on the pitching.
"We've shown the ability to hit the long ball," he said. "We have several guys in the lineup who can get you back in the game or separate yourself in one at-bat.
"As a whole, we're a much better defensive club than we've been in the past."
The Padres batted .290 in Cactus League play, outhomering the opposition 36-34.
The pitching staff's 6.35 overall Cactus League ERA was a concern in spite of difficult conditions (dry air, hard infields and winds blowing balls out of the yard).
In Monday's 4:05 p.m. PT season opener -- weather permitting -- Peavy engages the Giants' Schmidt in a duel of right-handed aces.