from MLB.com

Reggie Sanders pauses. He thinks back over all the teams he's been with -- seven stops, now, in a 14-year big-league career. There aren't many guys who have played with more teammates, or seen more styles, than Sanders.

And Sanders can't come up with anyone who wore a dirtier hat than current teammate Steve Kline. To find anyone who even rivals the St. Louis lefty reliever, Sanders has to go back over a decade to the days of the "Nasty Boys," when he was a rookie outfielder in Cincinnati and Lou Piniella managed the Reds.

"The closest would be Norm Charlton," said Sanders, after deliberating for a good 20 seconds. "But at this particular point, yes, [Kline] is the dirtiest of the dirt. He is the premier dirty dog."

The dirty cap is a curious phenomenon. It's more common to pitchers than hitters, who have their own analog in the grimy batting helmet. Different guys do it for different reasons.

Kline wears a grubby, disgusting cap as a tribute to the coal miners from his Western Pennsylvania home. Kline's teammate, Julian Tavarez, also wears a hat that borders on filthy, thanks to his habit of wiping his hand up there between pitches.

Then there's Dodgers closer Eric Gagne -- Kline's nominee for the dirtiest of them all.

"My hat size is right between sizes," Gagne explains. "And I have trouble finding hats that fit with my glasses. So I get a hat one-half size too big, then I shrink it down. That's why it gets stained. If I use a big one, the glasses don't fit right. And once I get the hat just right, I don't want to change it because it's a hassle. Then it gets dirty.

"But I've got my reasons."

They all do.

From Houston's Craig Biggio to Anaheim's Vladimir Guerrero to the Phillies' Jim Thome to about two-thirds of the Red Sox (or so it seems), the filthy, sticky batting helmet is a trademark. Some organizations frown on the practice, but for the most part, it's tolerated. It's habit for Biggio.

"For me, personally, I just didn't like it clean," said the Astros outfielder. "I just liked it the way it was. Some guys, it just seems like they're adding stuff on there just to add it on there. Mine, it was just accumulated over time. If it got dirty, it got dirty. Some guys look like they're kicking stuff on it, just throwing the pine tar rag on top of it."

For Guerrero, it's more of a practical matter.

"I do it when it's cold so I can get pine tar on my hands easily," Guerrero said through an interpreter. "I don't really think it's too big of a deal. Nobody really comments about it on our team, but the fans do. They're always yelling at me, telling me to clean it. But it's part of my routine."

The problem, if there is a problem, is that pine tar is sticky. And when a helmet with pine tar on it meets the ground, well, things stick to the helmet. It's basic physics, or chemistry, or something like that.

On the flip side, Guerrero may have one advantage from the pine tar.

"If he gets hit in the head with a pitch," cracked Angels bench coach Joe Maddon, "the ball will probably stick."

And then you've got Kline, who is one of the lefty-est of the lefty, to go along with the dirtiest of the dirty. His cap has become such a calling card that in 2002, the Cardinals held a Steve Kline Hat Day promotion, where they gave out caps pre-marked with dark spots.

"I do it for all the hard-working people back home," he says, then explains how exactly such a nice, clean red cap can get so grungy so quickly.

"In Spring Training, I just get it dirty," he said. "The guys on the team grab it, throw it around, beat it up, do all kinds of things to it. I don't do it every day. I don't go out and beat the living hell out of it every day.

"I have guys spit on it, stomp on it, throw it around. I have kids spit on it. On picture day, I'll throw it on the ground and let the whole team wad on it."

It's such a phenomenon that ESPN has even run a feature on the Kline cap. But he insists that it's not about drawing attention to himself. And in fact, the loquacious lefty was reluctant to be interviewed for this story, considering his cap's dirt quotient something of an overdone issue.

"I just want to make a tribute to my family and friends back home," he said. "They always say, 'Don't forget where you come from.'"

Sage advice. But so is this: Don't mess with these guys' lids. Biggio tells a story from some years back, when a clubhouse attendant in Pittsburgh went to clean off his helmet. Biggio got there in the nick of time, but not without a scare.

"I just told him, just make sure you don't do No. 7," he said.

And if he had?

"Five years ago, I probably would have freaked out," Biggio admits. "Nowadays, what are you going to do? Oh well. I've mellowed."

Must be the hat.

Matthew Leach is a reporter for MLB.com. MLB.com reporters Alyson Footer, Ken Gurnick and Doug Miller contributed to this story. This story was not subject to the approval of Major League Baseball or its clubs.