After the game Friday, Ruiz was admitted to Thomas Jefferson University Hospital for tests. Phillies assistant general manager Scott Proefrock said Ruiz would undergo more tests Sunday, but it appeared he did not suffer a concussion.
Phillies manager Charlie Manuel said Ruiz would probably return Tuesday or Wednesday at the earliest.
Ruiz was hit by a piece of Jason Kubel's broken bat in the eighth inning Friday. On Saturday, Ruiz said he wasn't feeling well and declined to comment further.
"We didn't want to DL him," Proefrock said, "because we don't think it's going to be that lengthy of a process."
The Phillies chose Sardinha, who was hitting .254 at triple A, because Paul Hoover has been on the disabled list with a left knee injury. Hoover was with the Phillies earlier in the season when Ruiz was hurt.
Sardinha, 30, has played in 31 major-league games over four seasons. He hit .097 in 12 games with Detroit in 2009.
Mathieson was demoted after only one outing with the Phillies, an unimpressive two-thirds of an inning in which he allowed two runs Friday. But Proefrock said the move wasn't predicated on Mathieson's work.
Technically, Mathieson was designated for assignment, but that's only because the Phillies had to place him on waivers to send him to the minors under an unusual roster rule.
There are four types of waivers, the rarest being optional waivers. They are required when a team wishes to option a player who has options remaining but is more than three calendar years removed from his major-league debut. Mathieson falls under that category; he made his debut June 17, 2006.
"He's sort of in limbo right now," Proefrock said.
Optional waivers are revocable, which means if any team puts in a claim for Mathieson, the Phillies can pull him back. Effectively, it's a paper move, and the Phillies expect Mathieson to report to triple-A Lehigh Valley sometime this week.
"We're very hopeful he stays in the organization," Proefrock said. "That's what our plan for him is."
It's an unusual roster move, which had Mathieson plenty confused. The righthander, who has hit triple digits on the radar gun while at triple A, has become a cult favorite among fans. He said he would spend the next few days working out at Citizens Bank Park.
After not appearing in a major-league game for three seasons, Mathieson pitched Friday. A day later, he was leaving the team.
"They said they expect me to be back up here and help them out," Mathieson said.
Jimmy Rollins (strained right calf) played shortstop in a rehab game for single-A Clearwater and was 0 for 2 with an RBI. Manuel said Rollins should return to the Phillies during the middle of this week. The manager said he would keep in close communication with Rollins when he returns to make sure he doesn't overdo it. "If he feels good," Manuel said, "then I'll probably let him loose." . . . Jim Thome's home run was his first against the Phillies. That means he has hit at least one home run against all 30 major-league teams. He's the 33d player in history to accomplish the feat. . . . Wilson Valdez homered in the second inning, the first home run he has hit since Sept. 26, 2004.