Geraint Thomas' hopes of defending his Tour de France title suffered a blow on Wednesday as his road captain Luke Rowe was thrown out of the race ahead of three decisive mountain stages to come.
Scroll down for full stage-by-stage guide & odds
Rowe was expelled along with Jumbo-Visma's Tony Martin after the pair clashed during stage 17 from Pont du Gard to Gap.
Video footage showed Martin almost riding Rowe off the road with Rowe appearing to grab the German, though the exact order of events was unclear.
Either way, it was enough for UCI commissaires to send both riders home and fine them 1000 Swiss francs (£812) each.
The decision could have huge ramifications in the battle for the yellow jersey, with Rowe a key rider for defending champion Thomas and Martin a big part of Steven Kruijswijk's team.
Thomas sits second overall, 95 seconds behind Julian Alaphilippe, with Kruijswijk in third, a further 12 seconds back.
After the stage, both Rowe and Thomas had sought to play down the incident but to no avail.
"To come here with this team, a bunch of good mates, I feel like I've let them down and of course let myself down," an emotional Rowe said after the verdict was handed down.
"We were both trying to do a job. Maybe we both overstepped the mark slightly, but it feels harsh to be thrown off the race, both of us. Neither of us deserve that."
Both teams stated their intention to appeal against the decision - but it was unclear whether they would be able to do so in time to keep their riders in the race.
Ineos team principal Sir Dave Brailsford called the decision "severe".
"It's nothing more than you see most days of the race," he said. "It's a pretty harsh decision.
"I think a yellow card would have been merited but a red card, for both riders, in fact, feels a bit severe to me."
Twelve months ago, what was Team Sky saw Gianni Moscon kicked off the Tour for punching rival rider Elie Gesbert on stage 15, but it did little to dent their dominance of the race.
Thomas is likely to feel the absence of his fellow Welshman more given their close friendship, although Rowe is not a climber and was expected to play a less pronounced role on the road in the decisive mountain stages to come.
But with the battle for yellow so close, this is still a significant setback for both Thomas and Kruijswijk, who were hoping to capitalise if Alaphilippe fades in the Alps, as is expected.
Alaphilippe had himself tried to calm the tensions on the road after the clash.
"I have seen something I don't like to see, riders too nervous and touching each other," the Frenchman said.
"Maybe they were scared that I would attack so I just tried to calm them down."
Rowe's exclusion is another setback for Team Ineos, who have not been able to dominate this year's Tour as they did as Team Sky in winning six of the past seven editions.
Head of performance Tim Kerrison admitted he had eyed the days to come as "good stages to defend on" but they must yet dislodge Alaphilippe, who has doggedly defended the yellow jersey for far longer than anyone expected.
Thomas is now hoping that three big days at altitude, starting with Thursday's brutal stage 18 which includes climbs of the Col de Vars, Col d'Izoard and the Galibier, all above 2,000 metres, is finally enough to shake Alaphilippe off after he showed his first signs of weakness in the Pyrenees.
"Obviously he wasn't great a couple of days ago," Thomas said.
"He's been racing well all race but you would think he'd be starting to get tired now. I guess teams will be thinking to try to make it hard all day. It'll be interesting, three big days."
The incident illuminated an otherwise predictably undramatic transition stage as the overall contenders eyed three huge days to come.
A 33-man breakaway - including Irishman Nicolas Roche of Team Sunweb - was left to contest stage honours, with Matteo Trentin attacking ahead of the final climb to solo to victory.
The European champion was part of a 33-man group which went up the road early in the 200km stage from Pont du Gard, and he broke clear on the approach to the final climb as the group began to splinter.
Trentin crested the Col de la Sentinelle with a 25-second advantage over Deceuninck-Quick Step's Kasper Asgreen and was able to extend that lead on the long descent into town to win by 36 seconds.
It was a third career Tour stage win for the Italian, and continued the most successful Tour in Mitchelton-Scott's history.
Daryl Impey won stage nine into Brioude before Simon Yates delivered on stages 12 and 15, meaning the team has more stage wins in the 2019 Tour than they did in all of their previous appearances since their debut as Orica-GreenEdge in 2013 combined.
"This win has a special taste after two that I got through bunch sprints," he said.
"I was making top 10 in all kinds of stages. Finally I won, it's a great moment."
Tour de France: Stage-by-stage guide
July 25, Stage 18: Embrue to Valloire (208km)
There may only be five HC climbs in the entire Tour, but two of them come in a single day as the riders tackle the Izoard and the Galibier before dropping down to the finish in Valloire. The stage winner should come from whichever group first crests the Galibier - appearing for the 60th time as the Tour's most regular Alpine venue - and this could be a decisive day overall.
July 26, Stage 19: Saint-Jean-de-Maurienne to Tignes (126.5km)
Stage 19 is a leg-sapping day designed to test the resolve of anyone planning a late move in the general classification. The Iseran - at 2,770m the high point of the Tour - comes in the middle of the stage and casts a long shadow before the shorter climb to Tignes offers an opportunity for attacks.
July 27, Stage 20: Albertville to Val Thorens (130km)
The last chance saloon for GC hopefuls does not look an inviting one. The final climb of the Tour is the 33.4km HC slog up to Val Thorens. If ever there was a Tour designed for a true climber, one with only a handful of time trial kilometres and four HC climbs in the last three days could be it.
July 28, Stage 21: Rambouillet to Paris Champs-Elysees (128km)
There are two big questions on the final day. Will the yellow jersey winner choose a few glasses of champagne or, as Geraint Thomas did last year, prefer a beer or two as they celebrate along the roads of the Parisian suburbs? And which sprinters will have survived the mountains in order to battle it out on the Champs-Elysees?