Guy will keep his name in the draft, meaning he won't return to Virginia for his senior season.
The 6-foot-9 forward served as a reserve for much of the season, but was promoted to the starting lineup during the NCAA Tournament.
Guy is the latest Virginia player to declare — Ty Jerome and De'Andre Hunter announced their intentions to enter the draft Monday.
The junior guard averaged 16.5 points per game during the NCAA Tournament as he helped lead Virginia to its first national championship.
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Duke claimed a 72-70 win in the end, but Virginia didn't go down without a fight.
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Cohn tweeted out a barb Saturday questioning the NCAA Tournament's one-and-done format.