Mark DeRosa now figures to play almost every day, until Michael Morse returns. (Toni L. Sandys/THE WASHINGTON POST)

With slugger Michael Morse sidelined and closer Drew Storen on the disabled list for opening day, the Washington Nationals must entrust crucial April roles to a pair of vital but utterly unexpected veterans: Mark DeRosa and Brad Lidge.

If either Morse or Storen prove to be more seriously injured, then DeRosa, 37, and Lidge, 35, who were signed on the cheap for their brains and experience, may be judged by a whole different standard: performance.

Just weeks ago, they were admirable oddities, oldsters bedeviled by injuries that might signal The End who’d be potential mentors for the Nats’ kids. DeRosa has a business degree from the prestigious Wharton School of the University of Pennsylvania and Lidge, a Notre Dame man, settled a Nats clubhouse argument by casually naming all 44 U.S. presidents in order.

General Manager Mike Rizzo and Manager Davey Johnson believe in IQ, especially in men who’ve played in 21 postseason series. But, much as they respect these vets, they never thought they’d be key cogs on opening day. Yikes.

“Looks like we might get a little more action,” said a smiling Lidge, who’ll split the closer role with Henry Rodriguez until Storen’s back.

If Lidge, healthy for the first spring in years, and his revitalized fastball stay as crisp as they’ve been in Florida, his ability to fill any late-inning role may give the Nats one of the deepest, most flexible bullpens in recent years.

DeRosa, his career almost dead last summer, now figures to play almost every day, in left field or at first base, until Morse returns. After that he’ll be platooned, at least temporarily, with Adam LaRoche at first base.

However, DeRosa’s potential — to produce a great deal or nothing at all, depending on his twice-repaired left wrist — opens wide possibilities. He can play five positions. He’s been red-hot, reaching base in 20 of 36 plate appearances in Florida with a 10-to-1 walk-strikeout ratio that exemplifies the kind of “tough out” that the high-strikeout Nats utterly lacked last year.

“I called Mark three or four times over the winter: ‘I’ll take you any way I can get you — 50 percent [healthy], 80 percent. We’ll work through it. I just want you,” Johnson said.

When DeRosa, who hit 44 homers in ’08-’09 as a super utility man, laced a through-the-wind homer off lethal lefty Jonny Venters this month, it sent a jolt through the Nats. DeRosa’s power was supposed to be extinct. Hadn’t he become a slap hitter? “I could hardly believe it,” DeRosa said.

It’s unrealistic to expect the one-man-bench DeRosa of ’02-’09 to return, much less the Lidge who had the perfect season for the ’08 Phillies — 48 for 48 in saves, including the World Series clincher — or even the Lidge of ’10 who saved 27 games with a 2.96 ERA. But, suddenly, both have a chance to show everything they’ve got left. Or not. That’s a corny plot — right out of 1930s baseball fiction for kids — that neither expected.

Both were signed as break-if-you-breathe-on-them discount items. What Rizzo and Johnson saw was resilience and baseball knowledge, plus the off chance one of ’em might get healthy one last time. What’s to lose?

DeRosa, who grew up in Passaic and has a Jersey accent as subtle as a tire iron, also played football at Penn. Almost every day, Ian Desmond, Danny Espinosa and others knot around him to talk hitting long before games. Lidge sees Storen, from Stanford, as a young version of himself: same embarrass-’em slider, mid-90s heat and a tendency to overanalyze.

Both vets accept their roles. But any glance at their history suggests a remarkable ability to confound sensible expectations. In the Ivy League, DeRosa considered himself “completely overmatched in class.” His day might start at 7 a.m. with a football meeting, followed by classes from 9 a.m to 1 p.m. , then a nap, a 3 p.m. baseball game and more football study after dinner. DeRosa sat in the front of every class, went to teacher’s office hours and often studied through the night. Every course was a battle, but he graduated.

“I felt I owed it to my parents,” he said. “They made a lot of sacrifices.”

Last year, he thought: “This might be the end of the road. . . . You get scared to swing hard. You don’t want to go down to the ground [in pain] on national TV.” Guilt ate him, too, after signing a $12 million deal with the Giants. “You let people down. You’re making all this money and not earning it.”

He went to the minors, came back pinging singles, being useful (.279). Maybe one last team would want him. Jayson Werth had the same rare wrist injury in ’06. Took two years to heal. But it did. The Nats took a chance.

In Lidge, the Nats see the same refusal to be reasonable. After a huge postseason failure in ’05 and a bad ’06, he was written off. After his ’08 glory comeback, ’09 was a disaster. Despite a $54 million career, we went to the minors — five stops — working his way back to the Phils to end with his head up. And in 75 games in ’10-’11, his ERA was 2.49.

So, Storen and others listen.

“As a reliever, you have to dumb yourself down. Just go out there and throw,” Lidge said. “Once it’s out of your hand, you have to let it go.”

Storen already quotes Lidge on facing the media after a blown save: “The sooner you face the music, the sooner it stops.” Storen has also taken another Lidge aphorism to heart: “Be smart about your body. Be dumb about your pitching.” That’s one reason Storen is being cautious with his inflamed (but not structurally damaged) elbow now.

Storen is the closer, period, as Lidge emphasizes. But, after allowing one earned run in seven innings with nine strikeouts and no walks, Werth said of Lidge: “The life is back on his fastball. He never lost his slider.”

“I still feel good about getting some chances in that inning,” Lidge said, not naming the ninth. “It’s great to have a normal spring training, build up arm strength and be myself again.”

DeRosa and Lidge will never again be the players they were in the ’00s. And it’s not their job to be. Another month of what they’ve shown in Florida might boost the whole Nats year and a season of it would be grand larceny — very grand. They don’t need to turn back the clock, just use the time that’s left. Luckily, they’re smart enough to know it — and then some.

For Thomas Boswell’s previous columns, go to