The Washington Nationals already possess the league’s best one-two punch at the top of their pitching rotation, and Jordan Zimmerman is a talented third option on top of that.

According to Fox Sports (via The Washington Post reporter Adam Kilgore), the Nationals added another arm to their rotation on Tuesday:

The Nationals have a deal in place to finalize perhaps the top starting rotation in baseball, agreeing to a one-year, $13 million deal with free agent right-hander Dan Haren, according to a person with knowledge of the deal.

The report notes that Haren must still pass a physical, but that “Haren said he has already taken a physical for another interested team, and he checked out fine.”

Washington is paying a nice chunk of cash here, but the reward potential is there. It’s good to know that his health appears to be on point, though, because that’s the only issue the talented right-hander is facing entering next season.

The Nationals need Haren to stay healthy, but they don’t need him to win 20 games. He adds stability to the middle and back end of the rotation, or more if either Stephen Strasburg or Gio Gonzalez were to get hurt.

Haren has always been a workhorse, and that’s important. He relies on his pinpoint control to dominate batters, and he uses his off-speed offerings to keep hitters off-balance rather than use a high-octane fastball.

He will slot in perfectly as Washington’s No. 3 or No. 4 starter, depending on where it views him in comparison to Zimmerman. Ross Detwiler will round things out in the rotation’s final spot, which could also turn out to be a good thing as he improves with experience.

When the playoffs come around, there’s nothing more important than pitching. It’s vital to have elite arms, but it’s also important to have quality reserves waiting in the wings. Pitchers are fragile.

Haren went 12-13 with a 4.33 ERA last season, but the healthy version of himself should be able to improve on that.

If he’s on, the Nationals hit a home run here. He’s dominant when he’s on, and that was as a top-end starter in his prime. Now, he can sit back, eat innings and help give the Nationals one of the league’s best array of arms.

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