The 28-year-old Valencia batted .188/.199/.299 in 44 games for the Twins and Red Sox last season, but is a career .316/.359/.472 hitter in 326 plate appearances against left-handed pitching. He is only a year removed from hitting .246 with 15 home runs and 72 RBIs for the Twins in 2011, when he led the majors in games played at third base (154) and topped the American League in assists for a third baseman (260). He was third in the 2010 AL Rookie of the Year voting after batting .311 with 18 doubles, seven homers and 40 RBIs in 85 games, posting a .351 on-base percentage.
He has never played a game at a position other than third base in his major league career. He is under team control until 2017, though he would be eligible for arbitration in 2014.
"His serious strength is he's very good against left-handed pitching," said executive vice president Dan Duquette. "He's a lifetime .316 hitter, with above-average on-base capabilities and average power. At his age, he should be able to regain the form that made him one of top vote-getters for Rookie of the Year a few years ago. He can play third and he's played first a few times (in the minors), but his real value is he's a very good hitter against left-handed pitching.
"He's young and a dependable fielder. He can help us with his bat, certainly against left-handed pitching, and he's capable in the field, also."
Valencia could be assigned to Triple-A Norfolk without having to clear waivers.
To make room for Valencia on the 40-man roster, the Orioles designated first baseman Joe Mahoney for assignment. Mahoney hit .265 with 10 homers and 56 RBIs in 132 games for Norfolk in 2012, and made his major league debut for the Orioles, going hitless in four at-bats over two games.