Complex sentence: He started the season as an understudy to goalkeeper Richard Lee, however during Lee's time out injured Moore put in some fantastic performances and cemented his place in the Brentford team under Uwe Rosler.
Split into simpler sentences: He started the season as an understudy to goalkeeper Richard Lee. During Lee's time out injured Moore put in some good performances and cemented his place in the Brentford team under Uwe Rosler.