Pat Tillman's Sundays usually consist of slamming into people like Randy Moss, Brett Favre, Donovan McNabb, Corey Dillon and Jerry Rice. The violent vortex of the NFL, as it turns out, is rather tame stuff compared to what the Arizona Cardinals' strong safety will do this coming Sunday.

"Man," Tillman said, "it's starting to dawn on me that this could be nasty."

	Pat Tillman will be running a half marathon in the Blackwater EagleMan Triathlon on Sunday.

Tillman will be one of 1,600 competitors in Cambridge, Md., for the Blackwater EagleMan Triathlon, a half-Ironman event that serves as a qualifier for the legendary Hawaiian Ironman in October. If all goes according to plan, Tillman will swim 1.2 miles in the brackish waters of the Choptank River, bicycle 56 miles through the Blackwater Wildlife Refuge and, finally, run 13.1 miles, past the historic home of Annie Oakley.

If all goes according to plan.

"We'll see," Tillman said in a theatrical tone. "I might just fall flat on my face. The challenge is to see if I can finish and get through it."

Why would a guy who is just catching his breath from all that battering and bruising on the football field seek to inflict more damage -- pain is probably the best word -- on himself? Because Tillman, 24, seems to be a pathological, clinically calibrated masochist. He disagrees with this amateur diagnosis, but triathlons, it must be pointed out, are very much a self-inflicted wound.

"Ahhhh," Tillman said, deliberately searching for the why. "Well, you know, we've got a long-ass offseason. Doing stuff like this gives me something to focus on. I feel like a bum not doing anything in the offseason. It forces you to stay on a schedule, keeps you from going out and drinking each night, doing something stupid."

Like, maybe, playing professional football? Tillman is smart enough to know better. He graduated summa cum laude from Arizona State in 3½ years with a 3.84 grade-point average. The fact is, Tillman's modus operandi has always been blissful denial.

At 5-foot-11 and 199 pounds, he was an undersized linebacker at Arizona State before matriculating across town to the NFL when the Cardinals made him the 226th choice in the 1998 draft. Tillman was Arizona's third pick in the seventh round, which means the Cardinals weren't exactly convinced he could make an impact at the ultimate level. Tillman, typically, didn't take the hint.

Down-sized to free safety, he had a terrific rookie season. Tillman started 11 games and was in on 92 tackles. When he lost the starting job to Kwamie Lassiter in 1999, he led the Cardinals' special teams with 30 tackles. As the starter at strong safety last season, Tillman's 222 tackles, as charted by the coaching staff, led all defenders.

Newly elevated defensive coordinator Larry Marmie was Tillman's position coach the past three years. He paused for awhile when asked to describe Tillman.

	“	Doing stuff like this gives me something to focus on. I feel like a bum not doing anything in the offseason. It forces you to stay on a schedule, keeps you from going out and drinking each night, doing something stupid. ”
		— Pat Tillman, Cardinals safety

"Well," Marmie began, "Pat's, uh, I don't know if different's the right word. I'd say Pat's a unique individual. He loves to compete. Obviously, his strongest asset in football is his competitiveness. To be honest with you, I'm not surprised to see him compete in anything."

Speed is not Tillman's forte. He is at his best crowding the line of scrimmage as a run stopper. But according to Marmie, he has become a credible pass defender. While many safeties seek out the slower tight ends in practice drills, Tillman usually takes a wide receiver.

The bottom line? Tillman is challenge-challenged.

Last year, looking for something to do with all that free time, Tillman decided to run a marathon. The fact that it was only two days after the Cardinals' mini-camp did not deter him. The fact that his calf muscle was tighter than a Titleist golf ball over the last 10 miles did not daunt him. Tillman finished in 3 hours, 48 minutes, which works out to 8-minute, 42-second miles -- impressive for a first-time marathoner.

"It's the idea of going out there and not knowing if I can do it or not," Tillman said from his home in Tempe, Ariz. "The marathon, I didn't know if I could do it or not. I thought I could. It's the same thing with the triathlon. The training is the whole thing. I've talked to some competitors, and they say in some ways the race is anticlimactic, compared to all the work you put in."

Since a friend sent him a 13-week Ironman training program three months ago, Tillman "doctored up" the workouts and has been averaging three swims, three bike rides and three runs per week in preparation for his first-ever triathlon. He'll compete for charity, including the March of Dimes and the ABC Hollister Foundation.

"I had no idea he signed up," said race director Robert Vigorito, when informed that Tillman was entered. "You just don't wake up and say, 'Gee, I think I'll go out and do a 70-mile race.' I'm glad he's prepared and in the race."

The run and the bike aren't the disciplines that concern Tillman. Running has been part of his training for years, and a bicycle was his primary means of locomotion at Arizona State. Swimming clearly will be his weakest link. Tight end Jay Tant, who made the Cardinals as a rookie, is Tillman's unofficial swim coach. Tant was a seven-time high school all-American and Ohio state champion in the 50- and 100-meter freestyle events.

"I had a couple of people look at my ... I don't know if I flatter myself by calling it a stroke," Tillman said. "When I decided to do this, I hopped in the pool and thought I'd start with 10-15 laps. I did five laps ... I was completely floored. Jay has really helped me out.

"I've heard it's a brawl -- people crawl all over you. I'm going to kick back a little and let everyone by me. This is my first swim, so I'll be the turtle."

In this age of specialization, there still are a few retro, two-career athletes. Moss, the Vikings' wide receiver, is moonlighting in the United States Basketball League. Kansas City tight end Tony Gonzalez is preparing for a second season in Southern California's summer pro hoops league. Deion Sanders, the erstwhile Washington Redskins cornerback, is laboring in the outfield for the Cincinnati Reds.

Tillman said he isn't doing it for the hype or the ego. He admits he has "no shot" at the 25 age-group qualifying spots available for the Hawaiian Ironman. That isn't the point, really. To paraphrase a certain shoe company slogan, he's just doing it.

"That's the difference with Pat and the average guy," Marmie said. "He feels he's more disciplined and more determined -- and he's probably right. I've talked about running a marathon, but I haven't gone out and done it. Pat has."

Said Tillman: "I'm actually real excited about it. Right about now you get a little bit nervous. If you weren't, it probably wouldn't be worth your time. I imagine it would be similar to football; after that first hit you're not thinking about it anymore."

"When I jump into the water, everything will be cool," he said. "Hopefully, I won't sink to the bottom."

Greg Garber is a senior writer for ESPN.com.