BOSTON (Ticker) -- The New York Yankees, losers of seven of their last eight games, shook up their bullpen today by activating righthander Jeff Nelson from the 15-day disabled list and making three other roster moves. Nelson, the righthanded setup man to closer Mariano Rivera, has not pitched since May 2. He went on the disabled list two days later due to inflammation in his pitching elbow. Nelson is 1-1 with a 6.10 ERA in 12 games, allowing 11 hits in 10 1/3 innings with 11 walks and 11 strikeouts. Last season, the 32-year-old was 5-3 with a 3.79 ERA and three saves in 45 relief appearances. To make room on the roster, the Yankees designated journeyman lefthander Tony Fossas for assignment. Fossas, 41, had no record and a 36.00 ERA in five games, surrendering four runs and six hits in one inning. New York also swapped righthanders with Triple-A Columbus, demoting Jay Tessmer while recalling Todd Erdos from its top minor-league affiliate. Tessmer was 0-0 with a 14.85 ERA in six relief appearances for the Yankees. Erdos was 2-1 with a 5.21 ERA in nine games, including four starts, for the Triple-A Clippers.  