When the Twins traded for Joe Nathan before the 2004 season, Mariano Rivera already had collected four World Series rings, five All-Star berths and 283 saves, already had established himself as one of the greatest closers of all time.

Nathan was a former Stony Brook University shortstop who had become a starting pitcher, then a setup man before the Giants dealt him to Minnesota. He owned one career save, and threw so softly during his first spring training in Fort Myers that the Twins considered trading for a replacement, like Chris Reitsma, before the season even began.

So this might sound like blasphemy, but since Opening Day 2004, the shortstop from Stony Brook has performed about as well as Mariano The Great. "I appreciate, definitely, what he has done," Rivera said Tuesday.

Nathan's entrance song is the straightforward rocker "Stand Up And Shout"; Rivera's is the ominous "Enter Sandman." Nathan features a handful of pitches that he constantly tweaks; Rivera relies on a nasty, late-breaking cut fastball that hitters know is coming. Nathan grew up in New York, Rivera in Panama. Nathan has pumped life into late nights at the dumpy Metrodome while Rivera has turned out the lights at Yankee Stadium.

If you transposed their career statistics since 2004, though, few would notice.

Since the start of 2004, Nathan is 21-11 with a 1.78 ERA, 221 saves and 0.918 walks and hits per inning. Rivera is 26-22 with a 1.98 ERA and 0.940 walks and hits per inning.

Nathan is 34; Rivera is 39. Neither is fading.

Nathan has converted 17 consecutive save opportunities and has not allowed a run in his past 20 appearances. For the season, he's 1-1 with a 1.35 ERA and 22 saves in 24 attempts.

Rivera became the second pitcher in baseball history to reach 500 saves on June 28. Since blowing two saves to begin the 2007 season, he has converted 90 of 94 opportunities. For the season, he's 1-2 with a 2.60 ERA and 21 saves in 22 tries.

Rivera, with 503 career saves, is pursuing Trevor Hoffman's record of 572. Nathan, with 222 career saves, is pursuing Rick Aguilera's Twins record of 254.

Nathan has trouble comprehending 500 career saves, even though he's averaging 39.8 saves per season as a Twin. "Impossible," Nathan said. "It's a mark that is unbelievable. I'm happy for him. As for me, it's light-years away. I've never been one to look beyond what I'm trying to accomplish today. One goal that's in my sights, when I look a little bit to the future, is Aggie's record here. That's about as far out as I can go.

"To me, 500 is ridiculous. To do it that long and stay healthy and be mentally tough enough to stay in this game and do that job for that long, those two guys deserve a lot of credit."

Rivera credits "The Lord," his family, a strong work ethic and plenty of rest for his success. "I don't drink or smoke," he said. "So I'm not out in the streets all night."

Nathan has studied Rivera's mannerisms. "I think the way he handles himself on a daily basis, when he gets a save, how his body language is, is something I've tried to copy.

"He's a guy that doesn't show a lot of emotion out there."

That, Rivera said, is exactly his intent. "You know when you have that competitor in you, you don't want to show those symptoms, symptoms of weakness," he said. "You don't want to look tired or weak, or that you don't have it that day. You don't want the opponent to see that."

When Nathan and Rivera pitch, what opponents most often see is a lot of handshakes. Rivera might be the best closer in history; Nathan might be the best in the game today.

"You appreciate guys like Joe because they just do their business," Rivera said. "He just goes out there, finishes it and goes home.

"I consider Joe a friend, and I respect the way he treats the game."

Jim Souhan can be heard Sundays from 10 a.m.-noon on AM-1500 KSTP. • jsouhan@startribune.com