Complex sentence: He then moved to Valencia, but was unable to establish himself as a regular in the starting eleven; he spent the second half of the 2008--09 La Liga season back with Racing on loan, for whom he scored 13 goals in just 19 matches.
Split into simpler sentences: He then moved to Valencia, but was unable to establish himself as a regular in the starting eleven. He spent the second half of the 2008--09 La Liga season back with Racing on loan, for whom he scored 13 goals in just 19 matches.