Ian Desmond poses during photo day at Space Coast Stadium in Viera, Fla., on Feb. 28, 2010.
Desmond is having an "exceptional spring" and the decision will "help the club this year and in the future," manager Jim Riggleman said.
Desmond was a third-round draft pick in 2004 and made his major league debut in September.
The 32-year-old Guzman is a two-time All-Star with a .271 career average in 10 seasons. He will get playing time at shortstop and second base, where he will take some at-bats from free-agent signing Adam Kennedy. Guzman never has played second base.
Also Sunday, Washington optioned outfielder Justin Maxwell to Triple A Syracuse. Maxwell hit .102 this spring -- 5 for 49 with 20 strikeouts.