The transfer window is open and, on the evidence of yet another careless attacking display, Chelsea need to dip into that £150m budget. Frank Lampard spent the majority of a scrappy contest bemoaning his team’s sloppiness in the final third and they paid a heavy price, suffering another stumble in the race to qualify for the Champions League when Alireza Jahanbakhsh came off the bench to rescue a deserved draw for Brighton with an astonishing bicycle kick.

Inconsistent and imprecise, Chelsea have not won successive Premier League games since the start of November and they could not complain after failing to withstand a spirited comeback from Brighton. Lampard, who was outmanoeuvred by Graham Potter’s tactical alterations, had much to ponder.

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It was a disappointing effort from Chelsea and the lack of incision should convince the club to take advantage of their transfer ban being lifted as speculation mounts about moves for Jadon Sancho, Moussa Dembélé, Wilfried Zaha and Timo Werner.

“It was an incredible equaliser but I think we deserved it,” Lampard said. “In the first half, if we are ruthless, the game is out of sight. We had opportunities to play people in who could score, to keep doing what we did in the first 20 minutes. We came off that slightly. We allowed them to feel they’re in the game and they’re a good team.

“The Christmas period has probably been a small showing of our season. Tottenham was a fantastic performance. Arsenal showed great spirit for a young group. Southampton, we struggled to break a team down and lost at home. Then today we should have the mindset to kill it and we don’t.”

Lampard was fuming and he stonewalled suggestions Chelsea could include Olivier Giroud as part of an £80m deal to sign Zaha from Crystal Palace. “The idea of that deal is something I have never considered,” the Chelsea manager said. “I won’t talk about Zaha because he is not a player of ours. If we have to do business we will do it in the way we see fit, to try to make us better, and that’s behind closed doors.”

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Nonetheless Chelsea’s forwards should be worried. Christian Pulisic flattered to deceive before being replaced by Callum Hudson-Odoi, who was just as ineffective on the left, and Willian offered little on the right. There was a lack of care in the decisive areas and Lampard grew irritable as the first half wore on, grumbling when Tammy Abraham spurned a chance to add to César Azpilicueta’s 10th-minute goal, shooting when he could have released Willian.

Not that it was all about the big team’s failings. This was Brighton’s first ever point against Chelsea and they might even have snatched all three after Jahanbakhsh’s stunner, only for Kepa Arrizabalaga to repel Neal Maupay’s low drive. Arrizabalaga would also make a fine stop from Aaron Connolly, whose introduction at the break gave Brighton more urgency. “I thought the players were amazing,” Potter said. “You go toe to toe with Chelsea and if you make mistakes they punish you. We had to adjust because our structure wasn’t so good in the first half. We got better.”

Facebook Twitter Pinterest César Azpilicueta taps in from close range to give Chelsea an early lead at Brighton. Photograph: Glyn Kirk/AFP via Getty Images

Chelsea, back to 4-2-3-1 after ditching their 3-4-3 system 34 minutes into their victory over Arsenal, started well, and took the lead after Reece James, included at right-back after a surprisingly quick recovery from an ankle injury, won a corner. Willian crossed to the far post, where Kurt Zouma headed down for Abraham to shoot from close range. Aaron Mooy blocked on the line but the ball broke to Azpilicueta, who turned in his third goal of the season.

At that stage, with Brighton uncomfortable in a midfield diamond, Chelsea should have pulled clear. But perhaps it was too easy. Chelsea’sintensity faded and Brighton threatened before half-time, Maupay teeing up Leandro Trossard to test Arrizabalaga.

Brighton, who will be without Dan Burn for two months after the left-backbroke his collarbone in a collision with James, were improving.

Potter jettisoned the diamond and he made another alteration during the interval, removing Yves Bissouma for Connolly.

The change meant Brighton were using a 4-4-2 and Potter was rewarded for throwing caution to the wind. Arrizabalaga denied Connolly but the breakthrough arrived when Lewis Dunk’s header led to Jahanbakhsh’s moment of magic. The Iranian winger had ended his long wait for a Brighton goal during last weekend’s win over Bournemouth and his second in two games means Chelsea must ask themselves some tough questions.