South African rider Daryl Impey claimed stage six of the Tour of Catalonia on Saturday as Alejandro Valverde extended his overall lead to 53 seconds over Alberto Contador.
However, three-time Tour de France champion Chris Froome plunged from second place to 31st after losing more than 26 minutes on the 189.7km stage from Tortosa to Reus.
Impey edged out Valverde in a sprint finish to the line to deny the Spaniard his third stage win of the Tour in 4hrs 34mins 14secs with Frenchman Arthur Vichot in third.
"I was just happy to have the legs for the sprint because I rode quite hard early on," said Impey.
"We moved (Adam) Yates up overall so to get the win on top of that is fantastic."
Yates moved up to fourth in the general classification behind Valverde's Movistar teammate Marc Soler, thanks to Froome's implosion.
The damage for the Briton was done early in the day as he missed out as a lead group of around 50 riders including Valverde and Contador formed on the first descent on an undulating stage after just 25 kilometres.
Froome, accompanied by his entire team, was unable to bridge a gap which grew throughout the stage leaving him out of contention.
"We made a big mistake. I'm not going to try and make an excuse, there is no excuse," said Team Sky sports director Nico Portal.
"It's a good reminder for us that it can happen to anyone. It's always bad when it happens, but maybe it's better to happen here, and we learn from it, than in some of the bigger races we will have this season."
In the lead group Valverde was well-protected by his teammates from any attacks by Contador as he edged towards a second overall win in Catalonia.
"We managed to catch out the Sky riders at the back," said Valverde.
"There was a lot of collaboration between the teams."
And he gained an extra six seconds on Contador thanks to the bonus time on offer from finishing second in the stage.
All Movistar riders were handed a minute's penalty for infringements by Jose Joaquin Rojas in Tuesday's team time trial.
However, despite that setback, Valverde's victories on stage three and five mean he just has to negotiate the 138.7km final stage around Barcelona on Sunday to add to his 2009 win in Catalonia.
"In theory there shouldn't be any problems, but there will be attacks for sure," added Valverde.