Australian Caleb Ewan was disqualified and race leader Patrick Bevin was hospitalised as the Tour Down Under erupted in controversy and drama.
Ewan won the fifth stage from Unley to Strathalbyn, but after a few minutes race judges relegated him from first place for a head-butting incident in the chaotic last kilometre.
His Lotto-Soudal team manager Mario Aerts said the decision to relegate him from the stage win was unfair.
The 149.5km stage went to Belgian Jasper Philipsen, who crossed the line second.
Overhead TV footage showed Ewan appearing to try to head-butt Philipsen as they jostled for position inside the last kilometre.
Ewan was relegated after an appeal from Philipsen's UAE team, whose sports director is Australian Neil Stephens.
"Of course, it's unfair to me," Aerts said.
"Caleb protects (himself), to not go in the barriers.
"Then he uses his head - he says 'I cannot use my hands, so what do I do to stay (upright)?'.
"I find it very 'light' - of course, head butts look spectacular, if they can't their hands, they have to use something else of their body.
"It's a heavy decision for a light thing to do."
Aerts added Lotto-Soudal were given no say before the race jury made the decision to relegate Ewan, who stays in the Tour.
Ewan did not comment after his relegation.
Aerts said he suspects Stephens made the appeal that led to the relegation, but added it was only a hunch.
This is Philipsen's debut WorldTour race and Saturday is now his first win at WorldTour level.
Ewan originally was ecstatic as he crossed the line.
He has had a tumultuous week in his first WorldTour race with the Lotto-Soudal team, following his split last year from the Australian Mitchelton-Scott squad.
Last Sunday, Ewan won the Down Under Classic warmup event.
Then he was caught out of position in stage one of the Tour, before finishing second.
Also at Saturday's finish, Bevin was in agony and holding his right side after
he was caught in a crash 10km from the finish.
Bevin bravely chased back with help from fellow CCC Team riders and rejoined the peloton with 3km left.
But he was also bleeding from wounds on his right knee and right elbow
Bevin was taken away by ambulance before the podium presentation and it is unclear whether he will start Sunday's last stage.
"He's a brave and gutsy guy - he went down hard," TV commentator Stuart O'Grady said of Bevin.
The New Zealander ended stage five maintaining his seven-second lead over South African Daryl Impey.
They shared the two intermediate sprints, meaning they gained five seconds on the climbers who will thrive on Sunday's summit finish at Willunga.
Australian star Richie Porte is in a group of contenders now 26 seconds behind
Bevin on the overall standings and 19 seconds behind Impey, the defending champion.