Hairston, 30, hit .210 with 10 home runs last season for San Diego, primarily as a backup outfielder and pinch-hitter. He will battle Nick Evans for New York's one remaining reserve outfield spot. Willie Harris, whom the Mets signed to a Minor League contract earlier this week, is a heavy favorite to make the team as a fourth outfielder and left-handed pinch-hitter.
Evans is out of Minor League options, meaning if he does not make the team, the Mets will risk losing him to a waiver claim. Jason Bay, Carlos Beltran and Angel Pagan are already entrenched as the club's three starting outfielders.
A veteran of seven seasons with the D-backs, Padres and A's, Hairston hit .258 with 34 homers over a two-year stretch from 2008-09, before struggling somewhat last season in San Diego. He is the brother of free-agent infielder Jerry Hairston Jr., and the son of former Major League outfielder Jerry Hairston Sr.