Originally signed by the Cubs as a non-drafted free agent in July of 2002, Rapada has gone 16-16 with 39 saves and a 2.89 ERA (92 ER/286.2 IP) in 208 career minor league contests (four starts). He has struck out 283 while walking just 110.
Rapada, who is available for tonight's 7:05 p.m. CT contest against the Seattle Mariners at Wrigley Field, will wear uniform number 50 and will be looking to make his major league debut.
Murton, 25, is hitting .252 (30-for-119) with a home run and eight RBI in 49 games for the Cubs this season. He was acquired by Chicago July 31, 2004, along with shortstop Nomar Garciaparra from Boston, in exchange for four players including infielders Alex Gonzalez and Doug Mientkiewicz.