The Italian finished second in the 2009 Giro but was stripped of the result and suspended after testing positive for CERA. Di Luca was previously implicated in the "Oil for Drugs" inquiry, for which he received a three-month ban in late 2007.
"If we want to talk in terms of percentages, we can say that when I won the Giro [in 2007] or two years ago, I was at 100 per cent and now I'm at 80 per cent," Di Luca said at Katusha's pre-race press conference in Borgaro Torinese on Thursday.
When pressed further on that frank assessment of his form, Di Luca sought to steer the conversation away from the question of doping, and instead blamed the drop off in his performance on the fact that he had spent the 2010 season sidelined from competition.
"It's not because I haven't trained like before or because I followed a different preparation. In my opinion, it's just physiological," Di Luca insisted. "Training by yourself without racing and then racing is very different. This Giro d'Italia will be useful to me not just for the rest of the season but for my whole career, as I will take on the effort of a three-week race again."
Di Luca was initially handed a two-year suspension after his positive test for CERA, but that sanction was reduced after he collaborated with CONI investigators by explaining doping methods. He returned to action with Katusha ahead of the 2011 season. While Di Luca says that he remains the same man as before, he insisted that he had learned from his mistakes.
"It's not that I'm so different to before as a man – I'm still me," he said. "Naturally, during the course of your life, you make mistakes. The important thing is to understand what those mistakes were and go forward looking to improve on where you went wrong. For the rest, I'm still me, the man you know."
Riding for Rodriguez
A big fish in a small pond at Cantina Tollo, and subsequently a Giro winner with Liquigas and a contender with LPR, Di Luca finds himself in uncharted territory as a domestique deluxe at this year's corsa rosa. With Joaquim Rodriguez set to lead Katusha's assault on the overall classification, Di Luca will have to content himself with a role as the team's road captain.
"I'll ride the Giro completely in support of Joaquim," Di Luca said. "With my experience, we can do a lot of things together. Joaquim is here to win the Giro and I'm here to help him. I can stay close to him in the fundamental stages and not just them and I can help organise the team and influence our race strategy during the race.
"Working for Joaquim is not a burden, it's not something I'm doing involuntarily. I would even have done it a few years ago too if I'd had a teammate who was capable of winning the Giro."
A peculiarity of Di Luca's role as team captain is that he will be the only Katusha rider not wearing a radio earpiece. "He prefers direct contact," his directeur sportif Serge Parsani joked. "He'll be doing kilometers up and down the road to come and talk to the car. Perhaps he'd do less with an earpiece."
Di Luca also admitted that in spite of his responsibilities to the team and the less than impressive form he has exhibited all spring, he will look to win a stage should the opportunity arise.
"If a day comes where I can do well in a stage, I will certainly look to take that chance," he said. "But it wouldn't be on a stage that was important for the overall, but rather on an intermediate stage where the classification wouldn't change."
Nonetheless, Di Luca reiterated that he arrives at this Giro with his personal expectations firmly in check, a far cry from his last, tarnished appearance in 2009.
"Of course I know I'm not at my best and I can't fight to win the Giro, but I'm fortunate that I have Joaquim beside me who can win it," he said. "For me, staying close to him and maybe bringing him to Milan in the pink jersey would be a great satisfaction."