Tremlett was named in England's 14-man squad on Sunday along with uncapped duo Simon Kerrigan and Chris Woakes as England look to close out the series 4-0, following their victory in the fourth Test in Durham.
Tremlett, who played the last of his 11 Tests against Pakistan in 2012, has been in England's squad for the past two Tests but not played and would relishing resuming his international career at his home ground.
With Tim Bresnan (stress fracture in lower back) and Graham Onions (broken finger) both ruled out of the match, Willis believes the England selectors will opt for Tremlett ahead of Middlesex paceman Steven Finn.
"With Bresnan out with that stress fracture of the back at the Kia Oval Chris Tremlet will come in. Surrey and England have been monitoring his progress very carefully this season," Willis told Sky Sports News. "He is now back to full fitness and bowling well."
Kerrigan, the 24-year-old left-arm spinner, has impressed for Lancashire and England Lions in recent seasons and could make his debut if England opt for a second spinner alongside Graeme Swann, while Woakes' chances of playing could depend on whether England decide to rest James Anderson.
Willis believes it is unlikely either will be involved in the final Ashes Test but says they both have promising international futures, although they may have to bide their time.
"I think he is probably going to go to Australia in front of Panesar," Willis said. "It is a little bit of a thankless task carrying the drinks around on these tours abroad because if Graeme Swann remains fit he probably is the best orthodox finger spinner in world cricket.
"So Kerrigan is going to have to wait in the wings for a little while. But he is now certainly the next cab off the rank.
"England are constantly looking for an all-rounder. Woakes is a very capable batsman. He bats up at No6 for Warwickshire so he could slot in for England below Prior at No8 and do a fine job.
"I am not sure yet on flat pitches his bowling is quite up to the mark. I would be very surprised if he was included in the final 11."