[4] Midway through his only season he was diagnosed with hepatitis A, being rendered unavailable for two months;[5] he made his return as a substitute on 4 April 2009, in a 0–1 home loss against Andalusia neighbours Sevilla FC.

Sisi scored a career-best five goals in 2011–12 (from 36 appearances) as the Castile and León side returned to the top flight after two years.

[9] In the subsequent off-season he joined CA Osasuna,[10] being hindered by two severe knee injuries during his spell, the last one contracted after only five minutes of the home fixture against FC Barcelona.

[13] In the following transfer window, he reunited with former Osasuna boss Jan Urban at Lech Poznań after agreeing to a six-month deal.

[19] Two years later, Sisi appeared against France in the 2005 UEFA European Under-19 Championship, as the national team failed to qualify for the final stages in Northern Ireland, losing 1–0 in the elite round.