The Nationals have claimed third baseman Carlos Rivero off waivers from the Phillies, per a team-issued press release. The 23-year-old Venezuelan hit .270 with 36 doubles, 16 homers and 71 RBIs between Double-A Reading and Triple-A Lehigh Valley in 2011. He was primarily a shortstop at the start of his minor league career in the Indians' organization, but switched to third base almost full-time last season when he joined the Phillies. The addition of Rivero gives the Nationals 37 players on the 40-man roster.