Nats acquire RHP Ian Dickson from Cubs for Henry Rodriguez (Karns optioned)

A week after designating right-hander Henry Rodriguez for assignment, the Nationals have traded the flame-throwing but inconsistent 26-year-old to the Cubs for minor league right-hander Ian Dickson. Dickson's numbers are far from impressive; the 22-year-old has posted a 6.88 ERA in 11 games (35 1/3 innings) for high Single-A Kane County this season. A 35th-round pick of the Cubs back in the 2011 First-Year Player Draft out of Lafayette College, Dickson has struck out 8.2 batters per nine innings this season, but he also has a 1.500 WHIP. Rodriguez originally came to D.C. in the winter of 2010 as the key part the Nats received in the Josh Willingham trade. The Venezuelan right-hander showed flashes of brilliance during his tenure with the Nationals, consistently hitting triple-digits on the radar gun and showing a wicked knee-buckling curve and a changeup that sat in the low-90s. He saved nine games for the Nats last season, but never found consistent effectiveness or control. Rodriguez had elbow surgery late last season and was given a chance to stick in the Nats' bullpen this year, but he allowed 14 hits and walked 16 batters in just 18 innings of work, and couldn't be trusted in tight ballgames. In his 111 appearances with the Nats over three seasons, Rodriguez hit four batters, threw 26 wild pitches, and walked 83. Dickson's ceiling doesn't appear to be too high, but you won't get much in return for a player who is so wildly inconsistent, especially when that player is out of options and has been dropped from your 40-man roster. Update: Manager Davey Johnson told reporters after tonight's 8-3 loss to the Rockies that the Nats will option right-hander Nathan Karns to Double-A Harrisburg in order to clear a roster spot for right-hander Ross Ohlendorf. Ohlendorf will get the start against the Rockies tomorrow night. The 30-year-old has a 4.27 ERA in 13 appearances for Triple-A Syracuse this season. Karns made three starts with the Nats in his first taste of the big leagues, posting a 7.50 ERA over 12 innings.