James McClean's late equaliser denied Chelsea the chance to record back to back league victories for the first time this season as Guus Hiddink's side were held 2-2 at home by West Bromwich Albion.
Chelsea twice took the lead through Cesar Axpilicueta and then again through an own-goal from Gareth McAuley after Craig Gardner had levelled.
But McClean's strike five minutes from time secured a point for the visitors and further diminished Chelsea's chances of reaching the top four.
Hiddink had reacted cautiously to Chelsea's improved recent form, refusing to make bold claims about what the club might achieve if his side can return to the form of last season.
The improvement in performances has been marked however, although West Brom manager Tony Pulis had launched a spirited defence of Hiddink's predecessor Jose Mourinho, insisting before the game it was disrespectful to suggest Chelsea's transformation was solely down to the change in manager.
Whatever the reason, last season's champions have been playing with more confidence and that was reflected in the way they started the game against a West Brom side looking to record three successive league victories for the first time in four years.
Back to back wins had moved Pulis's side up to mid-table, nine points clear of the bottom three coming into this game although last weekend's FA Cup draw against Championship Bristol City confirmed they have not yet shed their tendency towards inconsistency.
Pulis certainly sent out a clear message about his side's intentions when he named a back four made up of centre-backs.
But that was not enough to blunt Chelsea's spirited start to the game with Diego Costa moving past Jonny Evans before sending a shot wide in only the second minute.
Costa has been one of Chelsea's success stories since Hiddink took charge - but this game saw the best and worst of the Spain striker.
Initially, the forward looked sharp and dangerous and had another, better opportunity to score later on in the first half.
But once West Brom had worked their way back into the game after falling behind to Azpilicueta's opening goal, the frustration that grew throughout the Chelsea team found its focus in Costa who got involved in the kind of niggling spats that characterised his first half of the season.
Before then, though, the striker had played a central role in Chelsea's 20th minute opener, chesting down a long ball into the path of Willian who released Branislav Ivanovic on the right hand flank.
The right-back delivered a low cross across the face of Boaz Myhill's goal and left-back Azpilicueta was on hand, coming in at the far post to turn the ball home from close range.
West Brom had already shown they were capable of threatening Chelsea in the air with Craig Dawson and James McClean both testing Thibaut Courtois after out-jumping the Chelsea defence.
But the equaliser came from a long-range shot that owed much to the visitors' willingness to chase and press Chelsea deep in their own half.
On this occasion it was Darren Fletcher's determined work that forced an error from Pedro, and when the ball broke loose for Gardner, the midfielder finished superbly from 25 yards out.
Chelsea no longer looked so assured and they could have found themselves in even greater trouble had Salomon Rondon's shot on the turn not flashed over the bar.
And the frustration of the home side only increased when referee Anthony Taylor blew for half-time just as Chelsea were breaking.
Hiddink's side moved through the gears in the second period dominating territory and possession for long periods.
They forced the lead when Willian drilled a low cross towards the near post that was turned in by McAuley under pressure from Kenedy.
But with the game growing increasingly tetchy, McClean brought West Brom back into it at the death.