Bayer Leverkusen have told Chelsea that any deal to bring Andre Schurrle to Stamford Bridge this summer rests on Kevin De Bruyne moving in the opposite direction.
The Bundesliga club announced last week that they had opened talks with the Blues regarding a move for the Germany international, but insisted that no decision had been made as of yet.
The future of De Bruyne, who is enjoying a season long loan with Werder Bremen from Chelsea, has also being pulled into focus as a result of his parent club's efforts to sign the Schurrle.
De Bruyne's impressive performances in the Bundesliga have attracted a number of suitors, including Champions League semi-finalists Borussia Dortmund, who are now looking into the possibility of signing the youngster.
However, Leverkusen believe they are in control of the situation, and have urged Chelsea to offer Belgian international De Bruyne if they wish to keep their hopes of signing Schurrle alive.
"The transfer of Schurrle is a question of the total package. There are some more items and De Bruyne is one of them," Leverkusen's sporting director Rudi Voller told Sky 90.
"De Bruyne is a top alternative and can play a similar position like Andre [Schurrle]. If a good player leaves we've got to sign another good, or even better player."
The 21-year-old De Bruyne is yet to make an appearance for the Blues. Chelsea agreed to a fee in the region of £7m with Racing Genk in January 2012 to secure the Belgian's signature, before he linked up with his new club in the summer of that year. The attacking midfielder only spent a couple of weeks with his new teammates before making his loan move to Leverkusen, where he has scored six goals in addition to laying on a further nine for his teammates, helping his side to third place in the Bundesliga.
Chelsea have been heavily linked with a move for 22-year-old Schurrle since last summer, when Leverkusen reportedly turned down a number of bids from the Premier League side.