Harden struggled to start the game by giving up consecutive extra-base hits to Dave Roberts and Omar Vizquel, but quickly got back to form against Barry Bonds.
Harden got Bonds to fly out to left field on the first pitch and then retired Ray Durham and Rich Aurilia to end the threat. After giving up the double to Vizquel, Harden retired 12 of the final 13 batters he faced.
"Against the first few guys I threw a lot of fastballs," Harden said. "Then I switched it up and mixed them up."
Harden left the game after 59 pitches, 42 for strikes, and finished the spring with a 1.53 ERA.
Switch it up: A's manager Bob Geren said on Friday that Esteban Loaiza will start on Saturday at AT&T Park and will be moved to the No. 4 spot in the rotation.
That makes Joe Blanton the No. 2 starter, with his regular-season debut coming a day after Dan Haren opens against the Mariners on Tuesday.
Loaiza was slated to pitch on Thursday in Sacramento, Calif., but was bumped because of tightness in his trapezius muscle. The right-hander missed more than a month last year with a strain in the same muscle.
Loaiza's first regular-season start is scheduled for Thursday against the Angels, and if the 35-year-old hurler isn't ready to go, the A's will likely look within for help.
"We like our internal options within the organization," assistant general manager David Forst said. "We've got a number of guys that have been stretched out in camp."
The possible fill-ins to replace Loaiza would be relievers Brad Halsey and Chad Gaudin, or prospects Jason Windsor and Shane Komine.
The Buck stops here: With Dan Johnson's hip injury, the big leagues may be getting closer and closer for prospect Travis Buck.
Buck was expected to be a long shot coming into camp, with the A's signing Shannon Stewart and returning Johnson to first. But with Johnson and center fielder Mark Kotsay starting the season on the disabled list, Buck is likely to get a very long look in right field.
"Coming into Spring Training, they told me I wasn't going to have a chance to make the team," Buck said. "Now the injuries are starting to happen. It's a tough decision that they have to make on what to do with me.
"Coming in and knowing that I wasn't going to make the team took all the pressure off, and I just went out there is played. Fortunate enough, I had a good Spring Training."
If Buck plays in the outfield, Nick Swisher would return to first base, with Erubial Durazo being his backup. The A's could also choose to send Swisher to the outfield and have the 32-year-old Durazo in the starting lineup. Bobby Kielty is another choice for right field.
"That depends on how the final roster shapes out," Geren said. "We're still evaluating that. Both players are battling for potential roster spots and both had pretty good springs."
Buck is second on the team this spring with six doubles and is hitting .370 with a .574 slugging percentage. Durazo is third on the team with 14 RBIs and is hitting .283.
If Buck does travel with the A's to Seattle in their opening series, he will be able to give his family a pretty special gift.
Buck grew up in Richland, Wash., and could make his Major League debut about three hours from his hometown.
"That would be pretty cool," Buck said. "If not, I will go to Sacramento and we go to Tacoma the second week of the season. So either way, it will be good to see them."
Crow Hops: Geren said that he will have more information about Johnson's injury by the middle of next week. ... The skipper also said that Antonio Perez was not with the team on Friday because of a "non-baseball condition." Kielty was not in the starting lineup on Friday because he is still getting over some food poisoning. ... Geren said that Milton Bradley is still listed as day-to-day with soreness in his right side. Geren said that if Friday was a regular-season game Bradley would have started.
Up next: Loaiza is scheduled to make the start against the Giants' Matt Morris at 1:05 p.m. PT at AT&T Park on Saturday.