Sagan despite his suitability has not competed in the series of one-day races since 2013, opting instead for cobbles earlier in the European spring.
Speaking on the back of a silver medal performance at the Australian national road championships, McCarthy speculated the Amstel Gold Race specifically could be back on the star Slovak’s radar.
“...Rumour has it Peter may be doing Amstel so we'll see what happens there," the 25-year-old said.
McCarthy has previously outlined the Ardennes as a personal long-term goal and that doesn't appear set to change. He finished in the top 20 at both Amstel and Flèche Wallonne last season.
"I have a very similar (race) program to last year. After Tour Down Under I have an Italian one-day race and then I'll use Catalunya and Pais Vasco for the lead-in to the Ardennes Classics. I'll look to go well there again," he said.
Sagan's career-best result at Amstel so far has been a third place finish in 2012. He did not figure in another two appearances.
The 27-year-old, like McCarthy, will commence his 2018 WorldTour campaign at the Tour Down Under next week.
Sagan marked a quiet start to the season there last year and may do so again given Bora-hansgrohe has plenty of arsenal at its disposal. McCarthy, who finished third overall last year, is vying for the general classification in a squad that also includes Irish sprinter Sam Bennett as well as former Sky staple Peter Kennaugh.
"Peter (Sagan) will come and have some stage objectives. We've got Sam Bennett, who is probably going to go for some of the sprints and I'll hopefully go for the overall again.
"Peter is happy to float between those two to help us," McCarthy said. "I'm ready like I have been the last couple of years."