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.