Vasiliy Lomachenko is unsure how his long layoff will impact him in Saturday's lightweight unification bout against Teofimo Lopez.
Lomachenko (14-1) will put his WBA and WBO titles on the line at the MGM Grand while also bidding to win Lopez's IBF crown.
The Ukrainian is in action for the first time since August last year amid the coronavirus pandemic.
Asked how the longest layoff of his professional career would impact him, Lomachenko was uncertain.
"I'll check on Saturday, I don't know," he told a news conference on Wednesday. "I never stay one year outside ring, now it will be first time and I don't know."
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Lopez, meanwhile, has had a lengthy absence of his own after winning the IBF title against Richard Commey in December last year.
MORE: Lomachenko-Lopez fight date, start time, odds
"I feel great. For both of us, it's the same thing. We haven't had this long of a layoff," he said. "Even though during the time with quarantine and everything that was hitting, the pandemic, I was still working out, trying to stay on that as much as possible.
"I'm a big 135-pounder so I always stay in shape, always stay in shape. And I'm ready and I'm more than excited for this fight."
Lopez is defending his IBF title for the first time and his experience has been questioned ahead of facing Lomachenko. The 23-year-old, who is 15-0 with 12 knockouts, said he was ready for the challenge.
"I mean, hey, that's what it takes to go from a good fighter to a great, all-time fighter," Lopez said.
"You've got to do things like this and we spoke about this for a while now. Why am I going to go back on my word? I talk the talk and I walk the walk and I believe that I can and I know I will become undisputed world champion."