Complex sentence: At the end of the 2004 season, Juninho moved to Scottish club Celtic on a free transfer, making his debut in an Old Firm derby against Celtic's rivals Rangers FC, which Celtic won 1--0.
Split into simpler sentences: At the end of the 2004 season, he moved to Scottish club Celtic on a free transfer. Juninho made his debut in an Old Firm derby against Celtic's rivals Rangers FC, Celtic won 1--0.