Since he joined Chelsea in 2004, Petr Cech has been nothing short of superb.
Brought to Stamford Bridge by Claudio Ranieri for a bargain £7m from Rennes, Cech has saved the Blues on countless occasions over the last nine years.
Has there been a better Premier League goalkeeper over the last decade? Edwin van der Sar might run the Czech Republic international close, but the Dutchman only spent six years at the very top with Manchester United before retiring in 2011.
However, is the 31-year-old beginning to show worrying signs of decline? Is he simply suffering from a dip in form? Or could he be anxious about the prospect of losing his first-team place to Thibaut Courtois next season?
Whatever the explanation, it's clear that Cech hasn't been at his excellent best this season.
Against West Brom at the weekend he was certainly at fault for the second goal, while it could also be argued that he played a part in the Baggies' equaliser, too.
After making a point-blank stop, the veteran 'keeper took an age to get up, by which point Shane Long had already risen high to head into the back of the net.
The second goal, though, was inexplicable from Cech's perspective. Stephane Sessegnon shifted past John Terry before firing a relatively tame effort which Cech somehow failed to prevent going in.
All goalkeepers make mistakes, sure, but this is not the first error Cech has made this season.
Against Bayern Munich in the UEFA Super Cup, he should have saved Franck Ribery's optimistic - albeit well-hit - long-range effort, while he also allowed Sergio Aguero to beat him at his near post in last month's 2-1 victory over Manchester City.
It's unusual to see Cech make these types of mistakes, which is why they stand out so prominently. He's been ultra-consistent for years, but must get back to that level if he's to retain his first-team place at Stamford Bridge next season.
The reason: Chelsea have one of the best young goalkeepers in the world waiting to take his place.
Courtois has yet to play for the Blues, despite signing for the club in 2011, but the Belgium international has shown his immense class during his three loan spells with Atletico Madrid.
After managing Real Madrid for the last three seasons, Chelsea boss Jose Mourinho knows exactly how good Courtois is - and the thought to use him from the start of this season must have crossed the Portuguese coach's mind before he decided to loan him out for another campaign.
Is it possible that Mourinho has told Cech that Courtois will be in west London next season?
Regardless of whether or not that's the case, unless his form improves, expect to see Cech on the bench at the start of the 2014/15 campaign.