Baker has spent the past two seasons on loan at Vitesse in Holland and has made only one appearance for the Blues, back in 2014 in an EFL cup tie.
"I think so (Chelsea are missing a trick not having him)," Sinclair told Sky Sports.
"I think he's got a lot to offer. I spoke to Jody Morris who looked after him in his younger years and he's a true talent.
"Again, we go back to the Premier League, because of the pressures and because of the competition and how high the quality is, it's about opportunity and he's just not got that opportunity at Chelseaup to now."