The Spaniard had come into the team as a 19-year-old, just after signing from Barcelona in 2011, going on to make a decent 24 appearances in his first year of regular top flight football.
His next season was less successful, suffering a cruciate injury against Sunderland in December that would keep him out for the entire campaign.
Last year Romeu featured relatively regularly on loan at La Liga outfit Valencia, making 19 appearances as he eased himself back to fitness in his home country.
It was expected that Romeu would be signed permanently by Los Che, with the Blues midfield crowded despite Frank Lampard's departure after the arrival of fellow Barca graduate Cesc Fabregas, as well as the outstanding performances of Nemanja Matic since he re-signed from Benfica.
As it has turned out, Chelsea have decided to hang on to the former Spanish Under-21 international a little longer, perhaps conscious that his age, and his previous appearances hint at real potential that may yet come good at Stamford Bridge. Mourinho hasn't wasted any time involving the 22-year-old, with Romeu playing over 70 minutes in the club's 5-0 friendly win against Wycombe Wanderers yesterday.
Rumours of interest in both John Obi Mikel and Ramires from other clubs may well just be hearsay, but the retaining of Romeu would give Jose Mourinho back up were one of those more senior players to leave.