Barcelona want to sign Marcos Alonso this summer but have multiple issues, including around Chelsea's ownership situation, before being able to agree on a fee.
The 31-year-old has been talking to the Catalan giants and there's a belief that a deal can be done.
The Blues are also relaxed about letting their wing-back go as he enters the last year of his contract, which sees him earning £150,000-a-week.
Can Barcelona afford Alonso?
The Spanish giants can't currently afford to sign any players and their business this summer will be funded entirely on sales.
They have lined up two free transfers with Blues defender Andreas Christensen and AC Milan star midfielder Franck Kessie to join in the summer.
They are active in trying to cash in on several fringe players this summer, but could also sell one of their more regular starters with Frenkie De Jong attracting the interest of Manchester United.
The stance of the new Chelsea owners could be key for any deal to go ahead, with Xavi's side unwilling to pay the west Londoners any significant fee.
It's a similar situation to their ongoing pursuit of Cesar Azpilicueta, who remains a key target and could be allowed to leave for a nominal fee.
"So we are still in dialogue, we are also selfish, we are not responsible to solve any other club’s problems or to fulfil any other club’s wishes," Tuchel said this week.
"Given the fact we are already losing key defenders, it’s not the ideal scenario to think about losing Azpi, even if I can understand his personal point of view.
"At some point, if you are a legend, which he is, you deserve maybe, from me and the club, a second look at it, is there is maybe an exception from the rule; we are still in this process."
Who would replace Alonso?
Ben Chilwell is in good condition to play a part in Chelsea's pre-season and be the starting wing-back.
There are several other left-sided defenders at the club including Emerson Palmieri and Ian Maatsen. Both are able to play a role at Stamford Bridge but are attracting transfer interest themselves.
Emerson has long had interest from all the biggest teams in Italy but his successful loan spell at Lyon could broaden the options to include other Premier League clubs. Meanwhile, Maatsen is a target for Borussia Dortmund, according to reliable reports in Germany.
Signing a left wing-back isn't a priority within the first team but Brighton's Marc Cucurella is admired by the coaching staff. Manchester City are also interested in the former Getafe defender.