The Diamondbacks came closer to filling their center field vacancy as they closed in Wednesday on free agent Eric Byrnes. Byrnes, who agreed to what is believed to be a one-year deal worth about $2.2 million, will undergo a physical examination today in Phoenix. Byrnes, whom the Diamondbacks tried to acquire from Oakland last off-season, gives them a speedy, high-energy player who can man the center field position as prospect Chris Young continues to develop. advertisement The 29-year-old became a free agent last week when Baltimore did not offer him a contract, the end result of a poor second half of the 2005 season.