The idea of one day losing slugger Ryan Howard is worrisome, yet realistic, to Philadelphia manager Charlie Manuel. The veteran manager has seen National League All-Stars — and slugging first basemen — Albert Pujols and Prince Fielder depart for the American League and the lure of the designated hitter.

Howard, a first baseman who is 20 months removed from Achilles surgery and battling knee problems, seems to be a perfect candidate to follow that path when his contract expires in 2016. But there’s a scenario that could keep Howard and other aging, sore-kneed run-producers in the NL.

The new model of interleague play has ignited an argument about the future of the DH. Fifteen teams in each league — after Houston’s move to the AL West this season — translate to one interleague series at all times. Teams are traveling to the opposing league more frequently and forced to adapt with or without a DH.

The changes have led many in baseball to believe that the National League eventually will adopt the DH rule. If it does, the Phillies have a better chance of making Howard a lifelong Phillie.

“When you get to that point (in your career), it can be very enticing when you start thinking about it,” Howard said about the lure of the DH.

Manuel, like many traditionalists, is torn on the issue, believing that the longstanding differences of the two leagues is a positive. The idea that endless interleague play creates an unfair playing environment is just talk, Manuel said.

“It’s something to discuss and people might try to make an issue out of it. But at the same time (the DH) has been in effect for a long time,” Manuel said. “I think both leagues are balanced out.”

Maybe. Watching Twins pitchers Scott Diamond and Kevin Correia strike out three times in four plate appearances during their visit to Milwaukee at the end of May made Twins hitters think otherwise.

“A lot of the guys were joking when we were in Milwaukee and the National League, we’d rather see (a Twins DH), than (Mike) Pelfrey or (another pitcher),” Twins occasional DH Joe Mauer said. “Using that DH can really help.”

American League teams are asking pitchers to take more batting practice. National League teams are trying to turn pinch hitters into designated hitters. Neither is ideal.

“I don’t know which way they’re leaning. I know this sets up for some crazy stuff,” Twins manager Ron Gardenhire said. “Worst-case scenario, you’re in the pennant race, and now your pitchers have to go hit and run the bases. It wouldn’t be a lot of fun. I know National League teams do it all the time, but we don’t. So there’s a difference.”

‘Synchronize it’

MLB commissioner Bud Selig isn’t generally a fan of differences in the leagues. He’s rid the American and National leagues of separate presidents. He’s eliminated league-specific umpiring crews. And this year, he’s evened the number of teams in each league.

However, when it comes to the DH, the commissioner’s office hasn’t hinted of change coming.

General managers also haven’t spent much time discussing the DH.

“Whether it will be either disbanded or put into both leagues, that is going to come from the commissioner’s office,” Twins GM Terry Ryan said. “With interleague play taking place every day, it’s getting a lot more attention now.”

Leyland wants uniformity, referencing the NFL’s two conferences as examples.

“We’re the only sport where they have different rules,” Leyland said. “That doesn’t make sense to me. Synchronize it. Whichever way you want is fine. But at some point, you need to get it the same.”

Other solutions

The solution is eliminating the DH, said Twins pitcher Kevin Correia, a former National Leaguer of 10 years. He likes to hit. Baseball experts say that’ll never happen.

With so many big names in baseball settling into full-time designated hitter jobs, it’s becoming more about career longevity and money.

Billion-dollar TV deals, $100 million contracts, the love of home runs, are all reasons the DH is likely here to stay.

Other solutions mentioned to solve the debate include the addition of a 26th player for an interleague series, or making the DH rule a required piece of interleague play in every city.

“It gets brought up every few years. For a number of years, the American League was in favor and the National League was not. Until the powers that be reach a resolution, nothing will change,” said Bill Smith, who has played a role on the MLB scheduling committee and is Twins special assistant to the president and general manager. “Maybe the solution is to stay status quo.”