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The American League's designated hitter rule has been both embraced and vilified by the nation's baseball fans, their perceptions shaped largely by whether they favor offense or traditionalism.

The rule enters its 40th season, and controversy remains surprisingly strong considering this is one change that did exactly what it was intended to do. The DH was added in 1973 to increase attendance and run production in an era when pitching dominated.

Runs and attendance immediately shot up, and the American League became the superior league, winning eight of 11 World Series starting in 1983, and going 18-3-1 in All-Star Games from 1988 through 2009. Still, purists continue to express outrage, complaining that the DH stifles strategy, as if taking the bunt away from weak-hitting pitchers somehow threatens the game's integrity.

If the criticism has remained constant, the DH position itself has not, having morphed in ways few could have envisioned; the AL adopted the rule on a three-year trial basis and concluded it was so effective that it should be permanent.

The DH was at first a haven for aging or injured sluggers, or power hitters whose defense can politely be described as limited. Elements of that philosophy remain -- see the Twins and Justin Morneau, if the former MVP cannot return to first base.

But as the game has changed in the post-steroids era, so has the DH. Boston and David Ortiz are now the exception, with more teams, including the Twins, rotating position players into the DH spot.

With Jim Thome frequently injured the past two seasons, the Twins resorted out of necessity to the rotation strategy. A year ago four players -- Thome, Jason Kubel, Joe Mauer and Morneau -- got at least 13 starts, and 15 players in all had starts, tying for the AL high. Manager Ron Gardenhire said the master plan called for Ryan Doumit to be this season's primary DH, although Morneau's status likely will at least temporarily alter that.

As for his dream scenario, Gardenhire said: "It wouldn't be far-fetched to say Doumit could catch a couple days in a row, and give Mauer a couple DH days. Or put Mauer at first base, and DH Morneau a couple games in a row. We're going to put those guys out there, and keep those bats in the lineup."

Outfielders Josh Willingham and Trevor Plouffe could also figure in the platoon -- if Morneau doesn't claim it for himself.

The evolution of the DH certainly isn't over, because it may once again become a place to house aging sluggers. Having the DH available was certainly an insurance policy when the Angels signed Albert Pujols to a $240 million contract and the Tigers committed $214 million to Prince Fielder, both players formerly of the NL.

Those deals have some believing the DH might soon create an even greater chasm between baseball's leagues.

Milwaukee General Manager Doug Melvin said National League teams have a difficult time committing to more than six years for a free agent in the 30-year-old range because of the absence of the DH. Melvin's solution: Convince top free-agent pitchers to come to the NL, where the bottoms of batting orders are significantly weaker than in the AL.

"If all the [free-agent] hitters are going to the American League, we should be telling the pitchers to come over here," Melvin said. "Actually, I already see that happening a little bit."

Tougher than it looks

Denard Span has one career start at DH, last May 1 at Kansas City. It was plenty for him to realize just how difficult the job is.

"I know when I did it, I was overthinking," said Span, who went 0-for-5. "You pop up your first at-bat, you go down to the [batting cage] and you're thinking, 'I need to do this not to pop up again.' And so the next time up, I hit the ball into the ground. When you're playing, you don't have time to think. You head back to the outfield and you have to be ready to pick up your pitcher and make a play defensively."

Most players feel the same about the DH. Almost no one aspires to the job, and just how much the Angels and Tigers might benefit having Pujols and Fielder as DHs late in their careers is uncertain. Baseball analysts say that numerous studies show that when a player is too old to play in the field, he is too old to be an effective DH, the exceptions being Ortiz, Edgar Martinez and ex-Twin Paul Molitor.

"The pool of players who can just hit never evolved," said Brian Kenny, a baseball analyst who hosts MLB Network's "Clubhouse Confidential." "Everyone thought in the early '70s that players like [Tony] Oliva, [Harmon] Killebrew, [Hank] Aaron and [Orlando] Cepeda would be the first wave of great DHs. What we've found by and large is that when you lose your ability to play in the field, you lose your ability to hit shortly after."

As Span learned, many players simply find the mental demands of just hitting too difficult. Those that adjust are often, uh, unique in their skill sets. Tommy Davis, who won two NL batting titles, became Baltimore's DH in 1973 when knee injuries made it impossible for him to play in the field. Davis, a natural hitter, often took naps between at-bats and sometimes snacked on hot dogs. One day he raced from the clubhouse to the dugout to the batter's box with mustard dripping from his hands and spilling onto his uniform.

Doumit, at least, has an open mind about being the Twins' primary DH if Morneau is able to return to first base. In fact, the former Pirates catcher said it was one of the things that prompted him to switch leagues.

"This is an opportunity for me," he said. "In my career, I've been beat up a lot behind the plate, and getting out from behind the plate is a way to keep me healthy and keep my bat in the lineup.

"Of course, I don't know a lot about [the DH position]. This will be my first real taste of it, so I'm curious to see how it goes. Hopefully, it will be one of those things that grows on me."

Doumit has gotten a glimpse of what life as a DH is like during interleague games, an experience he recalls as "really weird." In 12 career DH starts, he has batted .159 with no homers and 13 strikeouts in 44 at-bats -- hardly what the Twins are looking for. Doumit's career average is .271.

Teams need flexibility

The rotation concept has reduced offensive DH production. American League DHs in 2010 batted .252 -- the lowest mark since 1990 -- with a .332 on-base percentage and a .426 slugging percentage, both the lowest since 1993. The batting average increased to .266 last season, but teams averaged 20 homers and 86 RBI from the position, compared to 28 homers and 94 RBI in 2006.

The move to rotating DHs at the expense of production appears, at first glance, counterintuitive. But other changes within the game -- such as pitch counts and bullpen specialists -- have had a domino effect.

When the DH came into existence, managers didn't chart pitch counts. Consequently, starters went deeper into games, and relievers were less a necessity. Teams at the time had nine- or 10-man pitching staffs. Now they generally keep 12, even 13 pitchers, which shortens the bench of a 25-player roster.

"I think most people don't want to be locked in to a guy who can only swing the bat," Twins GM Terry Ryan said. "They want a guy who can go out and play a position as well. ... [The DH] isn't for the Tony Olivas of the world. It's a revolving door, guys who can go out and play in the field."

Teams that try to return to the protoype DH can get burned if that player can't handle the job. A year ago, the White Sox paid big money for Adam Dunn, a subpar defensive first baseman and outfielder who had hit at least 38 homers in seven straight seasons in the National League before signing for $56 million over four years.

By all appearances, Dunn was born to be a DH, but the result was disastrous. He batted .159 with 11 homers and 42 RBI, striking out 177 times in 415 at-bats.

Dunn was an extreme case, but Kenny of the MLB Network said the average DH takes a 12-point hit on his on-base percentage, and pinch hitting doubles that.

"Anecdotally, players have said for years they can't get into the rhythm or flow [as a DH] to come off the bench and hit a 90-mile-an-hour fastball," Kenny said. "Turns out that's absolutely the case."

At least one Twins player isn't surprised.

"The good DHs, I tip my hate to those guys, to be able to be pure hitters," Span said. "That game I did it, it felt like I wasn't even in the game. Mentally, it can be a little tough. Like pinch hitting, it takes a special breed."

Maybe Span should have tried snacking on a hot dog between at-bats rather than heading to the batting cage.