Chelsea head coach Frank Lampard lamented his team's inconsistency and errors after suffering a surprise loss at West Ham in the Premier League, which opened the door for rivals Manchester United and Wolves.
Andriy Yarmolenko came off the bench and scored the 89th-minute winner as West Ham stunned London rivals Chelsea 3-2 on Wednesday.
Willian had netted a brace with a wonderful free-kick 18 minutes from the end to restore parity after Tomas Soucek and Michail Antonio had put West Ham ahead following the Chelsea star's 42nd-minute penalty.
But Yarmolenko's last-gasp goal lifted West Ham three points above the relegation zone, while ending Chelsea's six-game unbeaten streak in all competitions.
The result left Chelsea just two points clear of in-form United and Wolves in fourth position – the final Champions League spot – with six matches remaining.
Lampard vented his frustration afterwards, insisting Chelsea should have won at the London Stadium.
"It's the story of our season," Lampard told Sky Sports. "It's been a good season but there have been so many of these moments. We had an opportunity today to go through but you have to do every part of the game to get results.
"If you switch off or make one or two errors then you will encourage teams. Players have to show an extra mentality to get through these games.
"I get to see this group closely and I've seen us play great games then have moments where there's the opportunity to capitalise and that's the difference at the moment. We have work to do.
"There's without a doubt a good group of players in there but then when you analyse the consistency, you feel a game like this is coming. Again, that shows there's work to do.
"If we are opening up to try and score that winning goal then we have to be prepared to run back the other way and defend. And defend better.
"We are two points ahead of Manchester United, who have been playing fantastic and are on a great run, Wolves are having a great season and they're behind us, Leicester have had a great season and we're just behind them.