Chelsea are monitoring Bayer Leverkusen's Kai Havertz as they continue to assess their transfer market options in the belief Jadon Sancho will join Manchester United, sources have told ESPN.

- Stream ESPN FC Daily on ESPN+ (U.S. only)

The Blues retain an interest in Sancho but, as ESPN reported in April, they fear the 20-year-old favours a move to Old Trafford in a deal which could rise to as much as £120 million.

Chelsea head coach Frank Lampard is keen to overhaul his squad this summer with the club closing in on the £49m signing of Timo Werner from RB Leipzig in addition to the £38m capture of Hakim Ziyech from Ajax.

They are in the market for another attacking player -- while also pursuing Leicester City left-back Ben Chilwell -- and are keeping tabs on Sancho while recognising a need to identify alternative candidates.

Chelsea are one of several clubs to have been offered the chance to sign Philippe Coutinho from Barcelona, either as a loan or on a permanent deal, but have so far proved reluctant to match the £9m loan fee and £250,000-a-week wage.

A transfer would cost in excess of £70m, a similar fee to Havertz who is seven years younger and viewed as one of the most exciting talents in Europe.

There is, however, likely to be fierce competition for Havertz's signature with United, Bayern Munich and Real Madrid among the clubs interested in signing him.

Lampard views Havertz's versatility as a key factor given he can play as a No. 10, a central striker or out wide. His contract expires in 2022 but Leverkusen are increasingly resigned to losing him this summer.

Bayer sporting director Simon Rolfes said: "We don't know yet what will happen to Kai. We know that all the great clubs from Germany and Europe are after him and that he has the ability to play anywhere."