Chelsea's main problem this season has been putting the ball in the back of the net but for a long time at Stamford Bridge, the two main options in goal have also struggled to keep the ball out.
Both Edouard Mendy and Kepa Arrizabalaga have been considered the out-and-out number one choice for the Blues in recent seasons but neither would be considered among the best in the division, let alone the best in the world, on current form.
Kepa has had one of his best seasons in a Chelsea shirt with a 6.85 rating from WhoScored so far this campaign, which ranks him as the seventh-best performer at Stamford Bridge, yet it would be fair to suggest that he hasn't lived up to his £71.6m price tag, which saw him become the most expensive goalkeeper in football history.
Indeed, you only need to look at his limp showing against Real Madrid on Wednesday evening to realise why improvements are needed, with Chris Sutton having bluntly suggested he "should have done better" with the second goal.
Coincidentally, the Spaniard arrived in the summer of 2018 as a replacement for Thibaut Courtois, and after the Belgian helped Los Blancos to a 2-0 win over Chelsea in the Champions League quarter-finals this week, the Blues will surely be wishing they hadn't let him go so cheaply five years ago.
Will Chelsea regret selling Courtois?
Chelsea signed the Belgium international from Genk in 2011 for a fee of just £7.9m and he would spend the next three seasons on loan with Atletico Madrid in Spain, keeping 76 clean sheets in 154 appearances for the La Liga outfit.
He then returned to Stamford Bridge in order to dispel Petr Cech as the number one in between the sticks.
He would go on to make 154 appearances for Chelsea and established himself as one of the best goalkeepers in the world, so it was no surprise when Real Madrid came calling in 2018, with the west London outfit perhaps forced into a sale due to the shot-stopper's contract situation.
Courtois had just one year left on his deal at Stamford Bridge and had been vocal about returning to Spain to be closer to his children, but Chelsea were able to get just £35m for a player who was considered one of Europe's best in his position.
He has gone on to make 217 times for the Spanish giants, and 'dropped the greatest goalkeeping performance in Champions League final history' – as per GOAL – to win the tournament for the first time in his career last summer.
Praise has been forthcoming for a number of years now with former manager Zinedine Zidane full of adulation for the 6 foot 6 stopper in 2020, saying:
"Courtois has shown from the beginning that he is a great goalkeeper, he has always been among the best in the world."
Unsurprisingly, Courtois' performances across his time at the Santiago Bernabeu have seen his transfer value shoot up, with Football Transfers now suggesting that he could be worth as much as up to €73.2m (£64m), which represents a big increase on the £35m Madrid paid in 2018.
At just 30, the Belgian could easily remain Madrid's first choice for the significant future and considering Chelsea's own goalkeeper struggles in recent seasons, they will surely be wishing that Courtois had committed his future to Stamford Bridge back in 2018.