The Slovakian national champion and winner of the green jersey at the Tour de France took stages 1 and 3 in Colorado earlier this week and then came down with a stomach bug before stage 4 from Steamboat Springs to Beaver Creek.
"On the fourth stage I didn't feel very good," Sagan said after winning stage 6 in Fort Collins. "I had some problems with my stomach, but I don't know why. Maybe I had a little bit of a cold for my tummy. I recovered yesterday during the time trial, and today I felt very good."
Sagan's team chased down two breakaways during stage 6 before the 23-year-old freelanced his way through the closing kilometers and beat Luka Mezgec (Argos-Shimano) and Greg Van Avermaet (BMC) to the line.
Sagan started the Queen Stage on Thursday in third place overall, just 11 seconds behind leader Lachlan Morton of Garmin-Sharp. But after having to stop several times during the stage and struggling to the finish in 97th place, more than 16 minutes back, he dropped to 47th overall. He finished 53rd during the stage 5 Vail time trial, losing more than three minutes to stage winner and overall leader Tejay van Garderen (BMC).
But the rider who has staked his claim as one of the world's best sprinters was back on Saturday for his third win in Colorado, despite the fact that many other sprinters avoided the race. Even Sagan himself didn't think at the start of the week that he would have multiple opportunities to win.
"I am a little bit surprised, yes," he said. "I came here for maybe only being in the race to prepare for the [September World Tour races in] Quebec-Montreal. But now that I've won three stages, I'm very happy and a little surprised."
And Sagan has an even better chance of adding another stage win on the final day in Denver. Sunday's mostly flat stage is tailor-made for his fast finishing kick.
"I've won every one of the sprints here," Sagan said when asked about his chances for another stage win. "And tomorrow is not too long, only 100km, I think, no? So we'll see how my teammates feel and how I feel, and we can try also tomorrow."
Sagan will compete at the Tour of Alberta September 3-8 before the one-day races in Quebec and Montreal. Then he'll head to Florence, Italy for the world championships. Asked about his chances to win the rainbow jersey, Sagan threw the question back, saying, "Why not?"
"It's too difficult to say now whether I can win or not," he added later. "But I'd like to do well. I'm here to prepare for Quebec and Montreal, and after if I feel good I will go for the world championships, and we will see in the race. I don't know now."