Alberto Contador showed he was prepared to risk everything to win the Tour de France on Tuesday, crashing on the final descent as he tried to attack overall leader Chris Froome.
"He came through very quickly and struggled to keep control of his bike and crashed just in front of me," Froome said.
"I went off to the left slightly off the road so I had to unclip.
"He was taking too many risks down there. I personally think teams are getting desperate now, therefore taking uncalculated risks."
Froome still leads Dutch rider Bauke Mollema by 4:14 and Contador by 4:25 going into Wednesday's 32-km individual time trial between Embrun and Chorges.
Contador, whose right knee was bruised, was unapologetic and promised there would be more attacks to come.
"It is not a motivation to scare the others but sometimes you have to do it. I will continue," the 2007 and 2009 Tour champion told reporters.
The incident was reminiscent of the 2003 Tour, when Spain's Joseba Beloki, who was trailing Lance Armstrong in the overall standings, attacked on the same descent and crashed out of the race.
Armstrong avoided Beloki and in the process went down the hill across a small field to stay safe.
Briton Froome is expected to extend his overall lead in the 17th stage before two gruelling stages in the Alps. The first of them features the very tricky descent from the Col de Sarenne sandwiched in between two climbs of l'Alpe d'Huez.
UNDER FIRE
Having shown his rivals that he is almost impossible to drop in the climbs, Froome can expect to come under fire again on the downhills.
"I have seen this descent in training and also in the Criterium du Dauphine and it is a very dangerous descent," Froome said.
"The road surface is not great, I wouldn't say it's level. It's not smooth that's for sure and there aren't any barriers in the corners and if you miss a corner you will fall down a long way.
"I hope the riders are aware of this and they don't take unnecessary risks like they did today."
Contador, who said on Monday he did not care to finish second or 10th, also attacked twice on the climb to the Col de Manse on Tuesday but he was twice reined in so he took his chances on the descent to Gap.
"I hope that the crash doesn't affect me," the Saxo-Tinkoff rider said.
"The most important thing is to be relaxed now because tomorrow is an important day. My legs are getting better. I am confident I can put on a great show."
"The war goes on, we knew it," Sky sports director Nicolas Portal told reporters. "We knew it was a technical descent. Contador took risks and crashed. Until the end, they will seize every opportunity. Alberto likes aggressive races."
Movistar rider Costa won the stage after pulling away from the day's breakaway group to tackle he second-category climb to the Col de Manse alone.
He never looked back, staying ahead on the descent to win by 42 seconds.
Christophe Riblon and Arnold Jeannesson were second and third respectively as France continued to wait for its first stage winner in this year's Tour.
Photograph: Doug Pensinger/Getty Images