Left-back has been a troublesome position for Chelsea for years. Ever since Ashley Cole's decline, the Blues have struggled to get it right.
This season, things have been really rough for Frank Lampard, who has benched both Emerson and Marcos Alonso in favour of playing César Azpilicueta out of position, and the most concerning thing is that pretty much every fan agrees with that decision - Chelsea's left-backs are not good enough.
There's talk that both Alonso and Emerson could be on their way out this summer, so at least one new arrival is likely, and here are six potential candidates to fill the void.
Ben Chilwell (Leicester City)
In an ideal world, Chelsea would splash out on Ben Chilwell this summer. Unfortunately, we're not living in an ideal world, and there are a few stumbling blocks with this one.
The main concern is his price tag. Leicester are in no rush to sell, having tied him down to a six-year contract in 2018. They're still rolling in the Harry Maguire money and are on track to pick up some hefty prize money from the Premier League, so there has been talk of the Foxes demanding close to £80m to sell Chilwell this summer.
Obviously, shelling out that kind of money isn't easy, but it's not impossible. Chelsea still have the money from Eden Hazard's departure to play with, and if they decide that addressing their need for a left-back is their top priority, then Chilwell's name will be near the top of the list.
However, that's not the case. A source has confirmed to 90min that Chelsea are looking to spend big on a centre-back and a striker this summer, with a big-money spend on a left-back looking increasingly unlikely.
If everything else falls apart, a big move to sign Chilwell would work as a spirit-raiser, but there are bigger fish to fry these days.
Alex Telles (Porto)
For a few years, rumours of a future move to Stamford Bridge for Alex Telles have been slowly growing.The Porto man's agent told Sport Witness in 2017 that he felt as though Telles was destined to play for Chelsea, and that move could finally come to fruition this summer.
The 27-year-old will enter the final year of his contract this summer and has been rejecting any attempts to extend, and Porto don't want to lose yet another of their top stars for free. As a result, Telles is expected to be available.
He comes with a release clause of around €40m, but the Blues have been tipped to negotiate a discount because of his contract situation. Either way, he's probably a lot more affordable than Chilwell.
There are a few concerns about his defensive consistency, but Telles seems like the best option for Chelsea this summer. He's relatively cheap and is thought to want the move, and anyone who has watched Porto over the last few years will know how exciting he can be.
Marc Cucurella (Getafe)
Spanish youngster Marc Cucurella has long been tipped for greatness, and his loan from Barcelona to Getafe this season has only seen that excitement grow. Getafe are almost certainly going to trigger their option to sign him permanently, but that's only half the fun.
It's very possible that they could quickly flip Cucurella for a profit, and Chelsea are one of the sides who have been tipped to try and convince Getafe to do exactly that.
Given the 21-year-old's relative lack of experience, he would probably be available for closer to the €25m mark, which could prove to be the bargain of the century if Cucurella lives up to his sky-high potential.
However, it could also go the other way. Cucurella is still young and is yet to really play for a top side like Chelsea, so there are doubts over whether he is ready for such a move. It's a real risk, but the reward could be huge.
Achraf Hakimi (Real Madrid)
On the search for a new left-back, Chelsea are thought to have turned to Achraf Hakimi, who has spent most of his time during his loan with Borussia Dortmund playing at right-back. However, he is comfortable at left-back as well, so that's where this link comes from.
The 21-year-old has been excellent during his two years in the Bundesliga, but what the future holds for him is uncertain. Parent club Real Madrid may not want him back, given they still have Dani Carvajal, and a substantial offer might tempt them into selling.
He's another of those who would probably be a little too expensive, especially when you consider the fact that plenty of other top sides want to bring him in, but selling some of the unwanted squad players (including Alonso and Emerson) could raise enough money for Chelsea.
Hakimi's versatility would work in his favour - he's effectively a younger Azpilicueta - but any potential move for him might be a little too hard to pull off.
Blás Riveros (Basel)
If Chelsea spend big on other targets, there might not be a lot of money left over. The Blues have prepared for that eventuality by monitoring some cheaper options, and one of those is Basel youngster
Matt Targett (Aston Villa)
Another emergency target, Aston Villa's Matt Targett has been discussed by scouts at Stamford Bridge as a potential cut-price option this summer.
After a few reliable years with Southampton and Villa, Targett has proven to be able to hold his own in the top flight, and there's a good chance he could be available this summer if 19th-placed Villa suffer relegation.
Make no mistake about it, he would be nothing more than a quick fix at an affordable price, and Chelsea would likely look to buy another new left-back in 2021 once they have raised the money to do so. He's not the dream signing, but the Blues could do a whole lot worse than him.