The striker was knocked out in a collision with Canaries goalkeeper John Ruddy and was carried off on a stretcher wearing what appeared to be a breathing aid after receiving seven minutes' treatment at Stamford Bridge.

Drogba remained unconscious "for quite some time", manager Andre Villas-Boas said afterwards, revealing the 33-year-old had been taken to hospital.

The club later confirmed Drogba had undergone a scan at St Mary's Hospital, which showed nothing untoward, and said he was expected to be allowed home tonight.

Villas-Boas had no problem with Ruddy's challenge but said of the incident: "It looked pretty nasty.

"He lost consciousness completely on the pitch.

"I have to be very, very grateful, not only to my players but to the Norwich players and to my medical staff for reacting so quickly to a potentially dangerous situation."

Drogba's injury scare was just one of several dramas in today's game, which was ultimately decided by a controversial penalty.

Its award with 10 minutes remaining sparked a major flashpoint between the benches, with Norwich boss Paul Lambert shoving Chelsea coach Jose Mario Rocha after the latter entered the visitors' technical area to celebrate the spot-kick.

Describing Rocha as "the guy with the stopwatch on his neck", Lambert said: "I don't know who he is but he's flown right into our area.

"I'm not fluent in Portuguese so if he understands Glaswegian then he might know what I said.

"You don't do that - it's disrespectful."

Chelsea boss Andre Villas-Boas hit back, saying: "I know Paul was excited, not only with that.

"It's difficult to control your own emotions on the bench.

"But I would find it very, very strange if my technical staff would be disrespectful of Norwich and maybe they were just showing some emotions.

"If Paul can't handle that, I'm sorry - unlucky."

Lambert also took issue with the penalty award, which came after goalkeeper John Ruddy brought down Ramires.

Branding referee Mike Jones' decision "harsh", he added of Ramires: "I think he's lost control of the ball. He's actually going to ground before he's got it.

"But the referee's only got one take on it."

Ruddy was sent off and Frank Lampard scored the penalty to make it 2-1, with substitute Juan Mata sealing the victory on his debut in the closing seconds of what was 11 minutes of stoppage-time.

The scoreline flattered Chelsea - perhaps even the result - with Norwich enjoying as many clear-cut chances before going down to 10 men.

The game also cast further doubt on the Blues' title credentials after unconvincing performances in their opening matches against Stoke and West Brom.

Villas-Boas admitted his side lacked "fluency" in the first half but insisted they dominated the second, even though it saw Grant Holt cancel out Jose Bosingwa's sixth-minute opener after a horrible error from Hilario.

"The 1-1 came against the running of the game," Villas-Boas said.

"The impact of the 1-1 on the emotional part of the game is tremendous but, again, I'm very, very happy that the team is able to control their state of mind, to fight back, to show commitment and desire."

He added: "We looked better overall in a 90-minute performance."

Mata, who only completed his move from Valencia on Wednesday, made a real impact from the bench but Villas-Boas denied his side had lacked creativity before that.

He said: "All of the players are creative. They just express themselves in different ways.

"Other players are as talented as Mata is."

Revealing he had yet to make a fresh bid for Tottenham's Luka Modric, Villas-Boas added of his quest for more midfield reinforcements: "If it happens, it happens.

"If it doesn't happen, we have enough versatility to play with it."

The Portuguese also changed Chelsea's system today, playing a variation of a 4-4-2 with a midfield diamond.

That allowed Drogba to start alongside Fernando Torres for the first time under Villas-Boas, who said of their improved partnership: "They showed some positive signs."

Despite Norwich's defeat, there were also plenty of positives for the promoted visitors after what was the first big test of their Premier League return.

Lambert said: "I thought we were excellent, I really did.

"The penalty's turned the game. We could've been up 2-1, but I can't ask any more from the lads, the way they played. They came here and they thrived on it.

"We were up against a team that could potentially win the Premier League.

"I think Chelsea know they had a game."

Lambert, who lost Zak Whitbread to a hamstring injury he said may force him back into the transfer market, also hailed the performance of Holt after the striker caused Chelsea and England captain John Terry problems all afternoon.

"He's an old-fashioned number nine, which maybe a lot of people don't like playing against," said Lambert.

"John Terry's a world-class defender and I suppose you're better asking him how he felt playing against him."