Complex sentence: He won the Scottish Cup twice in this time along with his third SPL medal, the 2004--05 season proved to be Martin O'Neill's last at Celtic although Stiliyan Petrov would later join him at Aston Villa.
Split into simpler sentences: He won the Scottish Cup twice in this time along with his third SPL medal. The 2004--05 season was Martin O'Neill's last at Celtic, although Stiliyan Petrov would later join him at Aston Villa.