In the first half of last season, backup goalkeeper Asmir Begovic was asked to take over starting duties at Chelsea for an injured Thibaut Courtois. The former Stoke City veteran's showings confirmed his status as still a starting-calibre goalkeeper for a Premier League team, and he's thus drawn the attentions of Everton.
One of the names rumoured to be in Chelsea's plans to replace Begovic, if needed, is AC Milan goalkeeper Diego López. In fact, according to his agent Manuel Garcia Quilon, the Blues' interest is "real", though no deal has been reached yet.
"[A deal for Diego Lopez to Chelsea] is yet to be done, but the interest is real and concrete."
-Manuel Garcia Quilon; Source: Calciomercato.it
The 34-year-old made only nine appearances for the Rossoneri in the 2015-16 season, losing his status as first choice goalkeeper to youngster Gianluigi Donnarumma. The latest report says that signing López would make a transfer for Begovic a concrete possibility.
Chelsea's current position of having two starting-calibre goalkeepers is quite a comfortable one, though one that is probably not sustainable in the long-term. Barring another injury from Courtois, it's unlikely that Begovic will see much time on the pitch, so it might be best to let the Bosnian move on and bring in a veteran who can be useful if called upon, but won't demand as much playing time in return.