The Blues went into last weekend's Premier League fixture against Leicester City with Maresca having publicly stated that Reece James was their only injury concern.
However, when the team news at the King Power Stadium was revealed, Malo Gusto and Pedro Neto were both notable absentees from the squad.
After the game, it was revealed that Levi Colwill had only been passed fit shortly before the contest in the East Midlands due to illness, the centre-back going on to complete the 90 minutes.
While Colwill has been selected in the 21-player squad for the Conference League fixture versus Heidenheim on Thursday night, Gusto and Neto have been left in England.
Maresca comments on Gusto, Neto
Like Colwill, Gusto had been suffering from illness ahead of the game at Leicester, while Neto was said to have picked up "a problem" while representing Portugal during the November international break.
Nevertheless, speaking to reporters at a press conference in Germany, Maresca has indicated that both players should be available to face Villa at the weekend.
The Italian said, as quoted by football.london: "They will train with us. We do not want to take any risks for tomorrow's game but they should both be available for the weekend."
Marc Cucurella, Moises Caicedo, Enzo Fernandez and Nicolas Jackson have also been handed rests for the Heidenheim game by Maresca, while the likes of Wesley Fofana, Ben Chilwell, Romeo Lavia and Cole Palmer have not been registered for the competition.
A necessary move by Maresca
Maresca revealed at the same media briefing that Reece James was 'getting better and better" in his bid to recover from his latest hamstring injury.
That said, with a return not on the horizon in the short term, Chelsea need to keep Gusto fit for as many Premier League fixtures as possible.
Starting from Sunday, the West Londoners have three top-flight encounters in the space of a week, games with Southampton and Tottenham Hotspur following the meeting with Villa.
Axel Disasi is expected to feature at right-back against Heidenheim with Josh Acheampong still out of contention due to issues regarding penning a new contract.