Sorry it took someone longer than 28 minutes to respond to your question, very inconsiderate of us here at the cafe...
Not sure if there's a special tracker, but you can obtain the information from any stat site. Games (G) minus games started (GS) should be the number of relief appearances.
For example, Kuo has 3 starts and 39 relief appearances...http://www.mlb.com/stats/individual_sta ... rID=425539http://sports.yahoo.com/mlb/players/7649/career
LFoD '08 [1st/3rd], '10 [1st/3rd], '11 [1st/2nd], '12 [1st/1st], '13, [1st/2nd], '14, [1st/1st]
BRAL '09 2nd, '10 1st