The Washington Nationals have bolstered their strong starting pitching rotation by signing right-hander Dan Haren to a one-year deal worth $13 million, according to FOX's Ken Rosenthal. Haren had been with the Angels since 2010, when he was acquired from the Diamondbacks midseason.

Haren's effectiveness took a dip in 2012, as his ERA jumped from 3.18 to 4.33. Much of that can be explained by a drop in the number of ground balls he allowed and a leap in the percentage of fly balls he allowed that went for home runs.

In 2011, Haren was one of the American League's top pitchers. He tossed 238 1/3 innings, stuck out 192, accumulated 6.1 wins above replacement, and led the AL with 5.82 strikeouts per walk. Haren ended up seventh in the Cy Young voting, his best since a fifth-place finish with the Diamondbacks in 2009.

The $13 million is a slight raise from the $12.75 million that Haren made with the Angels last season.