Horner's first cameo of note came on the final climb to La Planche des Belles Filles on Monday, and he told Cyclingnews that his low-key showing to that point was due to a bout of illness and the distinct lack of climbs in the first week and a half of racing.
"How many climbs have we had? One day of climbing. We're on day 12 now and we've had one climbing stage and that's it," Horner said in Bourg-en-Bresse ahead of stage 12.
"Yesterday wasn't a good day, so at this moment I don't feel optimistic but in theory I do. It's possible to go top ten or win a stage. Everyone is so close in the top 20 that you could easily slide into the top ten."
Horner followed a course of antibiotics over the weekend in a bid to shake off an illness that has since afflicted his Lampre-Merida stable-mate Rui Costa. He was vague about the precise genesis of his ailment but was optimistic that he had shaken off its worst effects.
"It was just some kind of cold. We're riding through cow fields, it could have been something I picked up on stage 5, or a cold," Horner said. "It might not even be from the cold, it might be that every thing is dry, and there's more pollen so it could have been an allergic reaction.
"Rui and I had the same sickness and we both suffered a bit yesterday. I started the antibiotics a little before the Tour and I started them again before the rest day. Hopefully now that I'm off the antibiotics, everything returns to normal."
All told, Horner estimates that his condition heading into this year's Tour was "a couple of weeks" off the form he carried into his shock Vuelta a España victory last Autumn as a consequence of the repercussions from his heavy training crash in April. Recovering from broken ribs and a punctured lung has been more complicated, he said, that recuperating from knee surgery last summer.
"I had good mileage in training I just couldn't do effort because the ribs were so sore," he said. "If I trained too much early on, the lungs would expand, hit the ribs and puncture again. That happened to me a couple of times and I was back in the ER three different times. The last time I left the hospital was two months before the Tour de France so it was a little more difficult than last year."
Rui Costa remains the Lampre leader
The 43-year-old lies 16th overall, 7:33 down on maillot jaune Vincenzo Nibali (Astana) ahead of the Tour's entry into the Alps on Friday, while Rui Costa is just three places ahead of Horner, 5:34 off the overall lead. In spite of their proximity on general classification, Lampre's preordained hierarchy remains in place, although Horner is optimistic that he can climb into the top ten before Paris.
"Clearly you'll see me working for Rui but I can't do anything for Rui until we're on the last climb. Before then the team has to look after Rui and I have to look after myself," Horner said. "I don't expect any help from the team because my form's not 100 percent, and if Rui needs some help on the last climb there's something I can do for him but I'm not a strong enough rider to ride in the wind."
The premature abandonments of Alberto Contador and Chris Froome automatically removes two of the most aggressive climbers from the leading group in the high mountains, but Horner believes that their absence could play against Astana and make the race more difficult to control in the coming days.
"You'll see more attacking," Horner said. "When you had strong teams like Saxo, Sky and Astana, you had three teams who could chase down fifth place on GC if he goes. But now Astana are going to have to let some stuff go for sure, so there'll be more breakaways that go all the way to the line. And of course somebody in the top ten will be in one of those breaks sooner or later."
While Horner acknowledged that Nibali is the strongest rider in the race, he pointed out that the Sicilian was not operating on a wholly different level to his rivals for the maillot jaune, in spite of how it initially appeared at La Planche des Belles Filles.
"Nibali's certainly the best in the race at the moment but if you look at Plateau des Belles Filles, there was only a 20-second gap and it's not like the guys behind were all working together," Horner said. "When you go with 3k to go and you know the guys behind have played some games and hesitated a bit, 20 seconds is not that big of a number. If you've got six guys behind all working smoothly, maybe that number would have been five or six seconds, or maybe he's caught."