Allmendinger recovered from a poor start that saw him demoted to the back of the grid to win a race that saw 35 of its 95-lap distance competed under full-course yellow flags, with the worst incident taking out and injuring Sebastien Bourdais.
The Frenchman lost control of his Newman-Haas car on the exit of turn two on the opening lap, and in attempting to block the oncoming Forsythe car of Paul Tracy, they touched wheels, sending the Canadian skywards before coming down on top of Bourdais.
Tracy suffered two punctures such was the force in which it returned to terra firma while Bourdais, clearly dazed by carrying a ChampCar on his head, pulled off at the next corner and immediately requested medial attentions.
No word came from the Frenchman over the radio to Newman-Haas and anxiety kicked in. However, the medics soon confirmed that he was slowly regaining consciousness before being taken to hospital where checks found no serious injuries and was later discharged.
"I had no idea that Paul was there," Bourdais said. "His left front made contact with my right rear, and he went up in the air and landed on top of me.
"My head was knocked from side to side on the side rest, and I must have lost consciousness, because the next thing I remember was being stopped on the grass and the safety team running towards me," he added.
Allmendinger also made contact in the mayhem and dropped to the back. He and Tracy pitted for new tyres while Oriol Servia and Justin Wilson battled for the lead. The pit strategy and numerous other yellow flags would allow Allmendinger to scythe his way through the field and would capitalise on Wilson's late retirement with steering failure to take the win.
Junqueira would finish second while Servia inherited third when Mario Dominguez and Britain's Dan Clarke took each other out whilst fighting for the final podium place.
The Doctor fractured his right wrist and ankle in a high-speed fall in the opening practice session in Assen, and despite completing only four laps in Friday's practice session and qualifying last, the Italian fought back to finish a miraculous eighth.
A mixture of pain killers and pure adrenalin enabled Rossi to pick off the riders one-by-one, and on certain laps, the No46 was able to peel off lap times similar to those of the leaders. His eighth position was rewarded with eight points, but with championship leader Nicky Hayden taking the win, Rossi now finds himself 46 points adrift going into this weekend's British GP.
“We have a lot of work to do to improve the situation with my wrist and try to reduce the swelling and heal the bone as much as possible,” explains Rossi. “It would be better to have a month now to recover but we are racers and we have to go straight to the next race, which is a pity.
"Anyway I hope we can improve it as much as possible so that I can ride well at Donington," he added. "For sure I won't be at full fitness, but we have five days to improve. Colin showed that the bike is working really well so hopefully it will be like this at Donington also for both of us."
Donington has always been a happy hunting ground for Rossi, winning six of the past seven races there, and the Italian is hoping that his knowledge of the circuit will help him to pull off a strong result.
Donington is like a second home Grand Prix for me and I hope the fans give me all the usual support because I need all the help I can get right now," he said. "It's going to be a big challenge for me to stand on the top of the podium on Sunday, but as long as my hand continues to improve throughout the week, then I think we can try!
The Schu Factor
Renault's Fernando Alonso took his maiden Canadian Grand Prix victory at the Circuit Gilles Villeneuve on Sunday ahead of Michael Schumacher (Ferrari) and Kimi Raikkonen (McLaren) to make it four straight pole to podium wins; moving to 84 points to open his championship lead to 25 over Schumacher.
Defending champion Alonso became only the second driver in F1 history to finish on the top two podium steps in 10 consecutive grands prix - the first of course being Michael Schumacher himself with 10 successive top-two finishes.
"The race was quite difficult because off-line there was a lot of dirt and dust coming from the tyres," said Alonso. " If you go a little bit off-line you lose one or two seconds and we saw a lot of this type of incident throughout the race, so it was not easy to keep the concentration, leading the race with a nice gap but never confident on any of the laps.
"It was good, perfect all weekend. Obviously, without the safety cars, the gaps would have been much bigger, an easier race but you know the safety car sometimes helps you, sometimes not."
Renault team-mate Giancarlo Fisichella came through fourth after jumping the lights at take-off, losing his second on the grid to Raikkonen and incurring a drive-through penalty while Felipe Massa (Ferrari), pulled off a one-stop strategy to take fifth qualifying tenth.
The race of the day was surely David Coulthard who suffered a ten-place penalty after Red Bull decided to change his engine before the race; starting at the back of the grid. The Scot showed some of his old tenacity to hold on through the chaos and steal the final point from Jenson Button (Honda) after he ran messily through the final chicane; Coulthard lining him up on the inside before the final chicane.
NOT SO LUCKY THIS TIME
Last year Kimi Raikkonen inherited the lead late in the Canadian GP when Fernando Alonso ran wide exiting the final chicane; falling victim to the Wall of Champions and presenting the Finn a win.
But this year his run of bad luck began early when he lost several seconds in his first pit after the crew had a problem replacing his right rear; a clutch problem in his second costing him even more.
Falling twenty seconds off the pace luck again shined his way when, with ten laps remaining, the safety car came out - eliminating Alonso's twenty second lead. The Finn was behind the one-lap down Jarno Trulli as everyone piled up together, but the Italian was not paying too much attention when the safety car went in.
By the time he got messily past, Alonso had already put five seconds between them and with only two laps remaining it was unlikely that the seemingly quicker McLaren could take the Renault.
This was made certain when Raikkonen, in his second last pass through the hairpin, strayed onto the tyre debris and ran wide, allowing Michael Schumacher through for second.
"A tough race in a way but due to the beginning, it was sort of pre-decided and at a certain moment I just had to drive according to the situation which I did," said the seven time champion. "Obviously when the safety car came out, we went a little bit more on the attack and luckily we gained a position.
"I wished the race could have kept on going for a bit longer. We didn't have a perfect weekend but we managed to have a good result finally, so we go from here on."
ANOTHER HOME GP TO FORGET
Jenson Button had an awful time in his home Silverstone GP and Jacques Villeneuve had a similar fate in store, but at least with Button there was never really any hope.
Villeneuve was solid all weekend at the circuit named after his father but the same safety car that gave Kimi Raikkonen hope was the end of the Canadian's, brought on when he slammed into a wall after trying to take Ralf Schumacher Toyota on the outside into the back straight.
Ralf Schumacher also had a forgetful race after suffering from grip and brake problems all race long - also suffering a drive-through penalty for speeding in the pit-lane - finally retiring with seven laps to go.
Super Aguri's Takuma Sato had a minor run in with a wall and was forced to retire with only two laps remaining for him while Rubens Barrichello (Honda) and Super Aguri team-mate Franck Montagny also retired early.
ROSBERG STILL RAW
Juan Pablo Montoya (McLaren) was the next in line to complain about Williams rookie Nico Rosberg after Rubens Barrichello and his own team-mate Mark Webber criticised him after Saturday's qualifying when after just one lap the young German contacted the Colombian in the last chicane.
Montoya appeared to be through on the inside of the exit turn, but Rosberg insisted; forcing himself into the Wall of Champions.
After an nose-cone change from the contact, Montoya later scraped the same wall and retired with a rear-right suspension failure.