NEW YORK -- Could Andre Agassi be risking chronic health problems to remain on the path he is taking in his final U.S. Open?

The 36-year-old tennis icon is playing through constant pain in his lower back. The pain has plagued him for the past couple of years, and the Las Vegan has tried to combat the problem with injections of cortisone.

Agassi had four such shots last year and has had three this year, most recently Tuesday after his 3 1/2-hour first-round win over Romania's Andre Pavel.

On Friday, with his back still aching a day after a 3-hour, 48-minute, five-set victory over eighth-seeded Marcos Baghdatis of Cyprus, Agassi went back to a doctor for a shot of Toradol, a nonsteroidal anti-inflammatory drug, to ease his pain.

Agassi received another dose of Toradol on Saturday before his scheduled match against German qualifier Benjamin Becker, but it was postponed by rain. Agassi is scheduled to play at 8 a.m. (PDT) today, weather permitting, in the first match of the day at Arthur Ashe Stadium.

If Agassi wins, he will play his fourth-round match Monday afternoon, perhaps against fellow American Andy Roddick. Roddick meets Fernando Verdasco of Spain in Ashe Stadium after the Agassi-Becker match.

Tournament director Jim Curley confirmed that no day of rest will be scheduled for Agassi between matches.

"Players make requests all the time and we do our best to take everything into consideration," Curley said. "As for Andre playing Sunday and (then) Tuesday, the answer is 'no.' "

Meanwhile Saturday, Agassi was "doing as well as he can," according to his trainer, Gil Reyes. "He's not going to do anything to jeopardize his health long term, I can guarantee you that."

Agassi and his support team are in constant touch with Dr. Rick Delamarter, a Santa Monica, Calif., physician who has treated Agassi's back for the last couple of years.

"Dr. Delamarter is aware of everything we're doing here," Reyes said. "He's on top of it. Whatever Andre does, it's with his approval and knowledge."

According to Dr. Brian Hainline, chief medical officer for the U.S. Open, a player can have as many cortisone injections as he or she thinks they need. But there is a protocol that must be followed because tennis players are subject to drug testing.

As an Olympic sport, tennis is governed by the World Anti-Doping Agency. Paperwork must be filed with the Sweden-based WADA, which explains why it took six to eight hours for Tuesday's cortisone-injection process to play itself out.

Regarding the anti-inflammatory treatment Agassi received Friday and Saturday, because Toradol is not a steroid, it is not subject to WADA oversight and can be taken whenever Agassi wants.

"The prevailing medical opinion on pain medicine is an epidural injection can safely be given three times over four to six months," Hainline said of cortisone, originally developed in 1949 to treat inflammation but which has since been enhanced to reduce pain. Cortisone is a legal steroid in the sports world because it is non-anabolic.

"However," Hainline continued, "it depends on the dosage as well in determining how often you administer cortisone. If the attending physician believes additional cortisone injections are appropriate, as long as the guidelines are followed with WADA each time, then it's legal.

"The anti-inflammatory (Agassi was administered) was essentially Ibuprofen. It was Motrin or Aleve, only injected instead of taken orally."

Agassi has received between 40 to 80 milligrams of cortisone during his treatments and was given 30 milligrams of Toradol each of the past two days. But is it wise for him to receive multiple shots over such a short time span?

According to Dr. Jonathan Cluett, repeated injections of cortisone to the same part of the body can cause side effects over time, including permanent damage of the tissue.

"There's no rule to the limit of cortisone injections," Cluett wrote on about.com, a Web site dedicated to many topics, including medical issues. "But there are some concerns with repeated cortisone injections to one area of the body."

Agassi said after Thursday's match against Baghdatis that he will not do anything to risk his long-term health. Because he can take an anti-inflammatory daily without any danger, that may be the route he takes for the rest of the tournament, depending upon how he feels when he rises each morning.

However, doctors recommend that Toradol not be taken beyond five consecutive days to avoid the risk of potential peptic ulcers and internal bleeding. It is meant only for short-term use.

But whenever Agassi plays, he first has to be cleared by Hainline. All players with medical issues must be seen by Hainline before they're allowed to compete at the Open.

Longtime women's tennis star Martina Navratilova, who also will retire after the Open, spoke about leaving the sport when one wants to, rather than being forced to stop because of injury. She recalled having had about a half-dozen cortisone shots.

"You just don't want your body to give out on you. Andre has been struggling with his back for a few years now. You just want to quit on your own terms," said Navratilova, who turns 50 in October and is competing in mixed doubles and women's doubles.

"If he knows this is the last tournament, he's going for it with all guns blazing. With a back like that, it could be happening to you when you're 25. Not much to do with his age. But, yeah, it's frustrating. Hopefully he'll be able to stand up and keep fighting."

Agassi tried to get loose Saturday before his match was washed out. He hit balls for about 45 minutes indoors with coach Darren Cahill.

"It's a 50-50 thing, I guess," Agassi told reporters before leaving the USTA Billie Jean King National Tennis Center for his Manhattan hotel. "Having an extra day's rest may be a good thing for me. But it could mean playing two days in a row, which may not be such a good thing.

"Right now, I'm not looking ahead beyond this next match."

The Associated Press contributed to this report.