Complex sentence: Caragher first became a head coach with San Diego in 2007 and remained in that position until 2012; during his tenure, San Diego won three Pioneer Football League championships, including in his first and final seasons.
Split into simpler sentences: Caragher first became a head coach for San Diego in 2007 and remained in that position until 2012. During his tenure at the University of San Diego, the Toreros won three Pioneer Football League championships, including in Caragher's first and final seasons.