In addition to his Premier League contribution last season, Colwill played a major role as a substitute in the Conference League final and during the Club World Cup as the Blues won their first two major trophies under the current ownership.
His presence is key tactically, more than defensively but, crucially, Maresca believes that Colwill is his best central defender at build-up play from the back.
“When we build, we build with Levi in the middle,” said Maresca.
“Last year we played 64 games and we played all 64 games with either Levi or Tosin [Adarabioyo in the middle].
“Now Levi is out. The only other one that he can do that job well is Tosin. But we have Premier League, Champions League, with these kind of players.
“The rest, they can adapt. [Jorrel] Hato is a new one, he never played as the guy in the middle last season [with Ajax], so it’s not about being a central defender.
“Yes, [he is a] central defender but can he do that? It’s different. Also we have players that unfortunately, like Wes [Fofana] or Benoit [Badiashile], they have in this moment some [injury] problems.
“And this is the reason why I said that the club knows exactly what I think about central defenders.”
Josh Acheampong and Trevoh Chalobah having been trialled in Colwill’s role in wins over Bayer Leverkusen and AC Milan during a short two-week pre-season.
Chelsea are known to admire Crystal Palace defender Marc Guehi – who is is a target for champions Liverpool – but they are currently planning to strengthen their attacking options in the final two weeks of the transfer window, amid talks with Manchester United winger Alejandro Garnacho and RB Leipzig midfielder Xavi Simons.