He said: "If you shut shop at Stamford Bridge you're going to get picked off and lose by two or three anyway".
Sarri believes the 37-year-old still wants to play for another season but insists he will always be welcome at his "home" back at Chelsea in a coaching capacity.
The former Blues captain spent last season in the Championship with Aston Villa and is now a free agent.
Sarri, who took over from Antonio Conte earlier this year, spoke to reporters ahead of Chelsea's Premier League clash with Cardiff this Saturday and claimed the defender is welcome to join his coaching staff. If he wants to play for another season I think it's right he tries to play.
"We have to make decisions, which I do with the owner in terms of what we can do and what we can't do". I am very open with him because he is the history of the club.More news: Hurricane Florence: 'This One Really Scares Me,' Forecaster Says
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The Blues have been playing some great football this season and with top-of-the-table Liverpool travelling to Tottenham this weekend, Chelsea have a great chance to leapfrog the Merseysiders with a fifth consecutive victory tomorrow.
"John Terry is a fantastic player, a fantastic leader, he has got a lot to offer", Lampard is reported as saying in the Derby Telegraph. If he wants to help us, I'm very, very happy.
Terry left Chelsea in 2017 after almost 20 years at the club, where he won five Premier League titles.
"It's a hard game for everybody, against Cardiff", Sarri added.
"We need another step, I think, to be the same level".
While Emerson Palmieri, Davide Zappacosta and Ruben Loftus-Cheek have had knocks which could see them miss out. "Mentally after the break it is hard", he said.