Tom Dumoulin established himself as a Tour de France contender with another strong ride on stage 14, and Chris Froome is wary of the Dutchman heading into the final week of racing.
Dumoulin pushed Froome and race leader Geraint Thomas all the way on Saturday, coming home with the Team Sky duo as a gap began to open up in the general classification.
The three leading riders are separated by less than two minutes, with Dumoulin and Froome just 11 seconds apart.
Throughout the opening two weeks of action Dumoulin has rarely left Froome's side and finding a way to distance the Dutchman remains top priority for the defending champion.
"He's definitely [a worry], sitting in third place at the moment, just a few seconds behind me, I think he's our biggest threat at the moment," Froome told ITV Sport.
"There's still a good week of racing left, [we need to] keep chipping away, I think we're in a fantastic position with first and second in the GC which gives us options to play [with], as we did today."
The final kilometres of Saturday's stage saw Thomas, Froome and Dumoulin gain valuable time on the other GC contenders, with the former still leading the way by one minute and 39 seconds.
"No [problems today]. A big breakaway but no-one really from the GC so quite a steady day for us," added Froome.
"It was a very explosive finale, just a 10-minute climb but quite steep. As we saw there were gaps opening up all over the place.
"I feel good, for me it was always a goal to ride into this tour and I feel as if I've timed it well."
Race leader Thomas was also pleased with the way stage 14 unfolded, even if Primoz Roglic clawed back some seconds with a late breakaway from the peloton.
"We're satisfied," he told the Team Sky website. "Obviously Roglic got a bit of time back but it wasn't too much of a stress for us. It's nice to gain a bit of time on everyone else.
"The main thing was just staying with Dumoulin and just trying not to get too carried away and staying with the main guys. It was a good day.
"A lot can still happen. There's three big days in the Pyrenees still to come but obviously we're in a good position right now."