Via Baseball Reference (http://www.baseball-reference.com/g/guzmacr01.shtml), the player most similar to Cristian Guzman is Pat Meares, shortstop for the Minnesota Twins and Pittsburgh Pirates from 1993 to 2001. Meares' career stats (.299 OBP, .374 SLG, .673 OPS) are strikingly similar to Guzman's (.303 OBP, .382 SLG, .685 OPS).
Would you pay Pat Meares $16.8 million over four years, the money the Nationals are paying to Guzman? You might if your name is Cam Bonifay. Bonifay was the Pirates GM who signed Meares to a four-year, $15 million contract extension in May 1999. It was one of the disastrous contracts that saddled the Pirates with below-average players and crushing debt for years, and it was one of the contracts that got Bonifay fired.
In retrospect, no one would sign that contract.
Well, almost no one. Jim Bowden signed Guzman, a player whose stats are nearly identical to Meares', to a nearly identical contract.