"My first guess is that he would start on the DL," A's manager Bob Geren said. "We have nothing official on that. He couldn't pitch yesterday and he couldn't pitch today, and I don't see him pitching in a Major League game."
For most of Spring Training, the A's stayed away from the injury bug, with only Mark Kotsay scheduled to miss a good amount of time because of back surgery. Now, less than a week after first baseman Dan Johnson tore cartilage in his left hip, Loaiza may join him on the sidelines.
Loaiza was originally scheduled to start on Thursday in Sacramento, but was bumped because of back spasms in his throwing side. Loaiza said he didn't want to risk further injury by pitching on Saturday, and that he still has a chance to make a start on April 5 against the Angels.
"We talked about [the DL] yesterday," Loaiza said. "I wasn't really feeling that way. For me, right now, I'm just trying to get it treated. I will throw a couple of bullpens on Monday and Tuesday and we'll go from there. I don't know how long this is going to be."
Loaiza said that he's had back spasms before, but that they usually go away after two or three days.
"For the last six games, I've had this," Loaiza said. "Before that, I had nothing."
Loaiza describes the injury as a combination of pain and stiffness and has been receiving deep tissue massages.
The A's could go a few different ways if Loaiza isn't ready to start against Los Angeles. Geren said that Joe Kennedy could be moved up to the No. 4 spot and that Chad Gaudin, Brad Halsey or Lenny DiNardo could serve as the fifth starter.
Gaudin started on Saturday during the 6-4 win against the Giants and gave up four runs -- three earned -- over 3 2/3 innings. DiNardo came in after Gaudin and tossed 1 1/3 innings of no-hit ball.
"I'm ready for whatever they need," Gaudin said. "If they call me to start, that's what I got to do."
Gaudin started in Triple-A Sacramento last year before joining the A's bullpen in late April, and has also started for the Tampa Bay Devil Rays and Toronto Blue Jays.
"I've [started] my whole career before last year, so it's not that big of a deal," said Gaudin, who threw 66 pitches on Saturday and could possibly throw 80 if he starts. "You always want to start coming up through the Minor Leagues. I'm just going to keep the same approach and get outs."
Halsey threw three innings on Friday and started seven games last year when Rich Harden was placed on the DL.
"Whatever my role is, I just want to go out there and pitch well and help the team win," Halsey said. "Obviously, I like starting. In a perfect world, I would like to start 36 times. I would love to help the team out however I can."
The A's may also not need a fifth starter during the middle of the month because the team has April 12, 16 and 19 off.
New arrival: Todd Walker, who was signed to a Minor League contract on Friday, described this week as "getting thrown around in a washing machine."
Walker was released from the Padres on March 26 after hitting .282 in 44 games for the club last year.
"I got spun around a little bit," Walker said. "When you get released at the end of camp, it's very hard to find a job. I feel pretty fortunate. "
Walker started at first base on Saturday and batted fifth in the lineup. He's a better defensive choice at first base than Erubiel Durazo, and will give the A's more options in the infield and with pinch-hitting.
Walker, who has played in 49 games at first, feels that he has a definite chance to make the squad.
"If I'm just here for one game, then it's a lot for nothing," said Walker, who has mostly played at second base during his 11-year career. "Nothing is set in stone yet."
Too many catchers: On Friday, the A's traded Minor League catcher John Baker to the Marlins for infielder Jason Stokes.
Baker played in Triple-A Sacramento in 2006, batting .273 with four home runs and 38 RBIs in 83 games.
The A's are pretty high on Minor League catchers Jeremy Brown and Kurt Suzuki and were looking for another right-handed hitter.
Stokes was on the Marlins' 40-man roster this spring and was 1-for-11 with a double and two RBIs in eight games before he was sent outright to Triple-A Albuquerque on March 16.
He was originally drafted by Florida in the second round of the 2000 First-Year Player Draft and spent most of last year at Triple-A Albuquerque, where he batted .257 with seven home runs and 34 RBIs in 65 games. Stokes, 25, will be assigned to Triple-A Sacramento.
Baker was originally drafted by the A's in the fourth round of the 2002 First-Year Player Draft out of the University of California. The Bay Area native attended De La Salle High School in Walnut Creek, Calif.
Roster moves: The A's announced after Saturday's game that Durazo would not be on the Opening Day roster.
Durazo has the option to play in Triple-A Sacramento or leave the team.
Suzuki will start the season in the Minor Leagues, and Donnie Murphy was also optioned to the Minors. The A's have until noon PT on Sunday to make the final roster changes.
"We still have some decision to make this evening, and it could possibly carry into tomorrow," Geren said.
Short hops: Milton Bradley returned to the lineup after missing time because of pain in his side and went 1-for-3 with an RBI single in the third. ... Bobby Kielty also made his way back after food poisoning and went 1-for-2. Walker had two singles in the game but had a couple of problems with some bad throws at first. Eric Chavez's throw during the fourth inning was a little high and wide and tipped off Walker's glove. Walker also couldn't field a low throw from Kiko Calero in the sixth.
Up next: Joe Kennedy will make the last Spring Training start for the A's as they host the Giants and Noah Lowry. The first pitch is scheduled for 1:05 p.m. PT at McAfee Coliseum.
Ryan Quinn is a contributor for MLB.com. This story was not subject to the approval of Major League Baseball or its clubs.