The Nationals are fast knocking items off the winter to-do list. The latest move, according to a baseball source, is signing free-agent pitcher Dan Haren to a one-year, $13 million contract on Tuesday.

The deal, as always, is contingent on Haren passing a physical this Thursday. And that could be an issue for a 32-year-old who was traded last month only to have the transaction scuttled at the last minute. Haren was then still a member of the Los Angeles Angels and had been traded to the Chicago Cubs for relief pitcher Carlos Marmol. The deal was eventually called off.

Haren is a 6-foot-5 right-hander who would slot nicely into a rotation that already features Stephen Strasburg, Gio Gonzalez, who took third in the National League Cy Young voting last month, Jordan Zimmermann and Ross Detwiler. Haren has pitched for four different teams – the St. Louis Cardinals, the Oakland As, the Arizona Diamondbacks and the Angels – but has had success with all of them. He has made an All-Star team three times and finished fifth in NL Cy Young voting in 2009 and seventh in AL Cy Young voting as recently as 2011.

For seven consecutive seasons Haren pitched at least 216 innings. No current Nats starter in their young rotation has ever thrown that many. In his prime with Oakland and then Arizona, Haren posted ERAs of 3.07 (2007), 3.33 (2008) and 3.14 (2009). He struggled in Arizona early in 2010 (4.60 ERA), but rebounded in 14 starts with the Angels after a midseason trade (2.87 ERA). The next year he was excellent (3.14 ERA) and pitched another full season. This is a player who is a No. 2 starter, if not a borderline No. 1, in most rotations when healthy and at his best.

Of course, Washington doesn’t need that much from Haren if things go according to plan. Strasburg (3.16), Zimmermann (2.94) and Gonzalez (2.89) were all excellent last season and Detwiler (3.40) wasn’t too far behind. The Nats also expect to have Strasburg for a full slate of starts in 2013. No innings limit controversy this time around.

The medical issues for Haren include a stint on the disabled list in July with a sore back and a hip injury that, according to an email interview Haren gave to the Washington Post on Tuesday, he has dealt with since his days in Oakland. He managed just 176 2/3 innings, the fewest since his second year in the majors with the Cardinals in 2004 when he was still a rising prospect. Following the collapse of the Marmol trade, the Angels chose not to exercise a team-option for $15.5 million on Haren and instead paid a $3.5 million buyout.

If Washington’s medical staff clears him then the rotation is set and the Nats go about adding depth. It’s hard to believe they will be as fortunate as 2012 when the only real injury was to Chien-Ming Wang (hamstring) and that simply set the stage for Detwiler’s emergence anyway. Their luck was so good John Lannan – a pitcher with a career ERA under 4.00 – was stuck in Triple-A Syracuse virtually all season.

Haren struck out 142 batters in 2012 and walked just 38. He has always had excellent control and the hope is that a diminished fastball – once capable of hitting the low-90s consistently and now more often sitting in the high 80s – won’t spell the end yet for Haren as an effective force. Switching back to the National League should help there. But this is also a team where last year’s “fifth” starter was Edwin Jackson, who had a 4.03 ERA, tossed 189 2/3 innings and was due to make $13.3 million himself if the team chose to grant him a qualifying offer. It didn’t.

Haren’s ceiling is higher than Jackson’s, but there’s no guarantee he’s better, either. Health can be blamed for that 4.33 ERA with the Angels, absolutely. But if his back remains an issue or his old hip issues flare up then this may be what Haren is going forward. For $13 million over one season, and with a strong group of starters surrounding Haren, Washington’s front office believes that risk is worth taking. If he is close to his 2011 form, let alone any of his prime seasons, then this is easily the deepest rotation in the sport.

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