Chelsea capitulated in the second half against relegation-threatened Southampton by surrendering a two-goal lead to draw 2-2 in the English Premier League on Wednesday.
And Jason Puncheon completed a rapid Southampton counterattack in the 75th minute by volleying in the equalizer as the south-coast team rose three points clear of the drop zone.
"We didn't manage the game or have the control we were expecting," Chelsea manager Rafa Benitez said. "We didn't take our chances when we had them, which gave them hope they could score, and they did."
Chelsea remains third but Tottenham is only two points behind and the prospect of catching the Manchester rivals in the title race appears increasingly beyond this team. The Blues are six points behind Manchester City and 13 adrift of Manchester United.
"My idea is always to think about the next game," Benitez said when asked about Chelsea's title prospects.
Benitez, who is under contract only until the end of the season, was booed by disgruntled fans yet again on the day a long-term Chelsea managerial target, Pep Guardiola, was announced as the Bayern Munich coach from next season.
Benitez was coy on the impact Guardiola's decision might have on any hopes he had of securing a longer Chelsea contract, having replaced the fired Roberto Di Matteo in November.
"My job is to get three points against Arsenal," Benitez said.
Sunday's game will give Chelsea a chance to halt a miserable run at home that has also seen the team this month lose to Queens Park Rangers in the league and Swansea in the League Cup semifinals first leg.
Chelsea looked certain to capture three points on Wednesday when it was in complete control in the first half against a Southampton side it thrashed 5-1 in the FA Cup on Jan. 5.
The breakthrough took 25 minutes, though, with Benitez's decision to keep Fernando Torres on the bench justified as Ba netted his third goal since arriving at the start of the January transfer window.
Southampton created no danger near Cech's goal until Steven Davis struck wide but that was a rare threatening moment from the visitors.
Chelsea was pushing for the second goal, with Lampard missing the target from Mata's cutback and Oscar slicing the ball wide before the lead was extended.
Ramires hit the bar after pouncing on a loose ball and Hazard met the rebound and buried it in the net.
Chelsea was cruising until Southampton replaced Jay Rodriguez with Lambert in the 55th and the comeback was on three minutes later.
Lambert headed in his 10th goal of the season after connecting with Nathaniel Clyne's precise cross.
The closest Chelsea came to extending its lead was Lampard sending a free kick over until Stamford Bridge was silenced by Southampton's equalizer.
Luke Shaw, Southampton's 17-year-old defender, rampaged down the left flank unchallenged before crossing into the penalty area, where Ramirez clipped the ball across to Puncheon.
After teeing up the shot for himself, Puncheon volleyed beyond Cech with a fine finish in the 75th.
"We have to defend as a unit better, especially when you are winning," Benitez said. "That's something we have to improve."
The discontent among the home crowd only heightened when, four minutes later, fans' favorite Lampard was replaced by the misfiring Torres.
And the Spain striker missed his best chance to produce a winner when he missed the target after being set up by Mata.
Asked if the 50 million-pound (about $80 million) striker was affected by the jeers, Benitez said: "I think Torres is a professional ... he concentrated and tried to give his best."
Information from The Associated Press was used in this report.