Once a National League doormat, the Washington Nationals are suddenly one of the most exciting teams in baseball. A confluence of events — most recently the call-up of 19-year-old prospect Bryce Harper — have helped the Nats overcome a slew of key injuries and grab hold of first place in the National League East. But every good team needs a good rivalry to fuel the competitive fire during the dog days of summer. And now — finally — it seems the Nationals have found their foe. As Post columnist Tracee Hamilton wrote:

Now we’re talking. Now the Washington Nationals have a rival. A real rival, not an interleague, MLB-arranged, biannual blind date with the Baltimore Orioles, which despite their proximity was actually more of a long-distance romance. There are simply too many fans in this area who cheered for the Orioles for too long. That was always a non-starter.

No, the Philadelphia Phillies are it now. The “Take Back the Park” initiative was an embarrassment by its very necessity, although it was a success. But making a real rivalry is more complicated than an ad campaign. Here’s what you do. Take a former swaggering world champion. Put it in last place. Take the former division doormat. Put it in first place. Stir. Top with a cheeky rookie. Serve.

Phillies pitcher Cole Hamels helped push things forward by plunking Harper in Sunday’s series finale on national television, and then admitting he did it on purpose after the game. The move ultimately resulted in a relatively inconsequential five-game suspension for Hamels (he won’t miss his next scheduled start), but it lit a fire underneath Nationals general manager Mike Rizzo. As Adam Kilgore reported:

Nationals General Manager Mike Rizzo responded to Cole Hamels’ admission he drilled Bryce Harper on purpose last night in harsh terms, saying MLB should suspend Hamels and calling out Hamels as “fake tough.”

“Players take care of themselves,” Rizzo said after I called him this morning. “I’ve never seen a more classless, gutless chicken [bleep] act in my 30 years in baseball.

“Cole Hamels says he’s old school? He’s the polar opposite of old school. He’s fake tough. He thinks he’s going to intimidate us after hitting our 19-year-old rookie who’s eight games into the big leagues? He doesn’t know who he’s dealing with.”

Rizzo said player safety should take precedence and Hamels should miss at least one start.

[Late Monday afternoon, Major League Baseball announced that Hamels has been suspended for five games.]

“With all the bounty [stuff] going on in professional football, the commissioner better act with a purpose on this thing,” Rizzo said. “Players have a way of monitoring themselves. We’re not here to hit people and hurt people.

“He thinks he’s sending a message to us of being a tough guy. He’s sending the polar opposite message. He says he’s being honest; well, I’m being honest. It was a gutless chicken [bleep] [bleeping] act. That was a fake-tough act. No one has ever accused Cole Hamels of being old school.”

If nothing else, the weekend’s testy series should heighten the anticipation for remaining 15 meetings between the I-95 foes this summer. As Adam Kilgore wrote:

Find the fattest, reddest marker you can and circle May 21, the day of the Washington Nationals’ next game against the Philadelphia Phillies. In the hours after the final out of the teams’ three-game series at Nationals Park this past weekend, the rhetoric between the two clubs only intensified.

The Nationals had marketed the series as an appeal to Washington fans to “take back the park” from Philadelphia followers, who regularly made the two-hour trek to support their team. Sunday night, it became clear the enmity between the sides has extended to the players and executives as well.

Phillies pitcher Cole Hamels admitted after the game he had drilled Nationals 19-year-old rookie Bryce Harper with a pitch on purpose. Monday morning, Washington General Manager Mike Rizzo blasted Hamels, calling the move “classless” and “gutless” while labeling Hamels “fake tough.” Rizzo called on Major League Baseball to suspend Hamels, and by Monday evening, the pitcher had been handed a five-game ban.

Meanwhile, former Phillie Jayson Werth said he could hear Phillies fans taunting him as he walked off the field Sunday night with a broken left wrist, suffered after he slid to catch a fly ball. Werth underwent surgery Monday at the Mayo Clinic in Rochester, Minn., performed by Richard Berger, to repair a distal radius fracture. He will miss roughly 10 to 12 weeks.

In an e-mail to the Post, Werth, a member of the 2008 World Series champion Phillies, vowed he would return, motivated to keep Phillies fans from ever seeing another title parade.

“After walking off the field feeling nauseous knowing my wrist was broke and hearing Philly fans yelling ‘You deserve it,’ and, ‘That’s what you get,’ I am motivated to get back quickly and see to it personally those people never walk down Broad Street in celebration again,” Werth wrote.