Chelsea had goalkeepers Petr Cech and Carlo Cudicini taken to hospital after both were knocked unconscious in the champions' 1-0 win at Reading on Saturday.
Cech was being kept in hospital overnight under observation but Cudicini had been discharged, Chelsea later announced.
What proved to be an astonishing match at the Madejski Stadium began with Czech Republic keeper Cech caught by a challenge from Reading midfielder Stephen Hunt in the first minute and being carried off. Italian Cudicini took over, but collided with Reading's Ibrahima Sonko at the end of the game and needed treatment by paramedics before he too was taken off on a stretcher.
Coach Jose Mourinho said he thought Cech was lucky to be alive after being caught in the head by Hunt's knee, branding the Reading man's challenge "a disgrace".
Mourinho made it clear he expected action from the Football Association, though both Hunt and Reading manager Steve Coppell denied there was any malice in the challenge.
Chelsea stayed second in the table on goal difference after league leaders Manchester United came from behind to beat Wigan Athletic 3-1 in the day's early kickoff.
United and Chelsea have 19 points from eight games, three ahead of Portsmouth who beat West Ham United 2-0. Arsenal moved up to fourth with a 3-0 win over Watford.
Chelsea took the lead in first-half stoppage time when Frank Lampard's free kick through a packed area was deflected in by Icelandic defender Ivar Ingimarsson.
The champions had Nigerian midfielder John Obi Mikel sent off in the 62nd minute for a second booking, hauling down French defender Sonko.
But Chelsea held on and it was all-square in terms of players when Reading's Cameroon defender Andre Bikey was dismissed in the 83rd minute.
Cudicini was stretchered off in the closing stages, reportedly having been given oxygen and a neck brace. Captain John Terry had to play in goal for the final minutes of stoppage time.
The day's early action at the JJB Stadium was only four minutes old when Wigan left back Leighton Baines crashed home a 25-metre piledriver, giving keeper Edwin van der Sar no chance.
Though United took charge of the game, they had to wait until the 62nd minute before equalising through Serbian defender Nemanja Vidic, heading home a Ryan Giggs corner.
Four minutes later, Alex Ferguson's side were in front with a superb finish by French striker Louis Saha following a cross from Wayne Rooney, who had an excellent game after a difficult start to the season.
Norwegian forward Ole Gunnar Solskjaer wrapped up the points in stoppage time.
"There's a good momentum about the team at the moment and hopefully we can keep that going," Ferguson told Sky Sports.
The Scot was delighted with Rooney, who hit the bar in the first half, saying: "I think he was right back to his best."
Arsenal's victory at the Emirates Stadium moved them up to fourth on 14 points with a game in hand.
An own goal by Watford's Jordan Stewart set Arsenal on their way and captain Thierry Henry rifled home the second before teeing up Togo striker Emmanuel Adebayor to add an easy third.
Liverpool were spared defeat against Blackburn Rovers at Anfield by a Craig Bellamy equaliser against his old club in a 1-1 draw.
But they remain mired in mid-table after taking only a point despite plenty of second half pressure, having gone behind to a strike by South African forward Benni McCarthy.
Aston Villa striker Juan Pablo Angel missed a penalty and scored an own goal in the space of three calamitous minutes in their 1-1 draw with 10-man Tottenham Hotspur and Middlesbrough edged Everton 2-1.
Portsmouth kept their remarkable start to the season going with a fifth win from eight games. Nigerian striker Nwankwo Kanu got his sixth league goal of the season before substitute Andy Cole added a late second at Fratton Park.
West Ham's defeat left them in the relegation zone, above Watford and Charlton Athletic, while Sheffield United earned a point with a 0-0 draw at Manchester City.