Rui Alberto Costa of Portugal celebrates as he crosses the finish line to win the sixteenth stage of the Tour de France cycling race over 168 kilometers (105 miles) with start in in Vaison-la-Romaine and finish in Gap, France, Tuesday July 16, 2013. GAP, France (AP) - Chris Froome preserved his healthy overall lead after a nervous finish to Tuesday's 16th stage, and then blamed his main Tour de France rival Alberto Contador for a downhill incident that could have ended their races. Portuguese rider Rui Costa won the stage with a solo breakaway, while behind him the subplot between Contador and Froome thickened with a few days left until the finish line in Paris. Although Froome is still more than four minutes clear of Contador, the British rider felt he could just as easily have ended up in hospital. "One little accident and it could be the end of your Tour," Froome said. In my opinion it was a bit dangerous from Alberto to ride like that, it's not good. On the final descent down from the Col de Manse, Froome and Contador were undone by a sharp right turn as the Brit chased after the Spaniard. Froome went off the left side of the road and had to plant his left foot on the ground to stop from toppling off completely. Contador also lost balance and hit his knee on the ground before quickly jumping back up on the bike. "It actually put me in danger because I had to go off the road to avoid him," Froome said. He couldn't control his own speed and crashed. Contador, the 2007 and '09 champion stripped of his '10 title for doping, defended himself. It was really difficult. In normal conditions I wouldn't have slipped like that, but it was very difficult terrain and the bike got away from me," he said. Sometimes you have to go for it, whether it's at the start or the end of a stage. The incident was reminiscent of the 2003 Tour when Spaniard Joseba Beloki broke his right arm, elbow and wrist after crashing on the descent from Manse. He lost control of his bike going into a turn at full speed and flew across the road. Lance Armstrong, stripped of his seven Tour titles for serial doping, was riding just behind him and had to take sharp evasive action, swerving off the road and then running across a small field before re-mounting his bike. "At the moment I'm trying to take as least risks as I can," Froome said. Everyone knows it's a dangerous descent and we've seen a lot of images from the past ... But I didn't think guys were going to take unnecessary risks there. Froome seemed to be more than a little exasperated, and his radar will be on red alert in the days to come. "All teams are starting to get desperate now and they're taking uncalculated risks," he said. In my mind this Tour is not over until I cross the final line on the Champs-Elysees. Meanwhile, Costa broke away on the 9.5-kilometer (6-mile) ascent to Manse - the last of the day's three moderate climbs - to secure the second stage win of his Tour career, after winning another hilly stage up to Super Besse ski station in 2011. He crossed the line 42 seconds ahead of Frenchman Christophe Riblon. "I knew exactly what I had to do, and every second that I gained going uphill was useful at the end," Costa said through a translator. Froome and Contador finished more than 11 minutes behind Costa, who is not considered to be a contender. About halfway up Manse, Contador attacked, but Richie Porte responded and got Sky teammate Froome back on Contador's wheel. Contador attacked again soon after and opened up a gap of about 50 meters (yards) before being caught, and then tried a third attack. Bauke Mollema could have gained more time but chose instead to wait for Froome and Contador after their mishap. Mollema remains second overall, 4:14 behind Froome, while Contador remains 4:25 back in third. Froome will look to extend that lead in Wednesday's time-trial - one of his favored disciplines - before three huge mountain climbs in the Alps. "It's a very hard day tomorrow with two climbs and two downhills," Froome said. You have to keep a bit of energy for the following days in the Alps. The 168-kilometer (104-mile) route started from the Provence village of Vaison-la-Romaine in the heart of the Rhone winemaking country. Early on, about 25 riders started to pull away but started to split open when Costa surged up Manse. "This win will make us happy," said Costa, whose teammate Alejandro Valverde dropped out of podium contention last week when he lost a lot of time on Friday's 13th stage after stopping for a mechanical failure. It's my victory, but it's also a victory for the team.