South Africa-born Pietersen is gearing up for his first county championship action since June 2013 after agreeing a new deal with Surrey.
The 34-year-old is determined to restart his Test career after he was sacked in February 2014, and Tremlett backed his county team-mate to achieve that feat.
“Maybe that’s the case that those changes open a door,” said Tremlett of Downton’s ECB exit.
“They were the guys who were in place that I guess made those rulings that he wasn’t going to come back and play for England.
“People have heard things from Colin Graves the last few weeks that he might have a chance of coming back.
“I guess it’s just wait and see, who knows what’s going to happen in the next few weeks, other positions could change within the England set-up.
“But I think Kevin knows he’s got a chance if he goes out there and scores runs.
“I think he feels he was harshly treated by being released from the ECB a year or so ago, so I think he’s got a point to prove and it will be exciting to see what happens.
“I don’t see why he can’t get back into the England set-up.
“There’s been a couple of changes over the last couple of days with England, and I don’t know what’s going to happen there.
“But I’m sure if he stacks up a lot of runs then people are going to be pushing for him to get back in the England side.
“It will be interesting to see how it unravels in the next five or six weeks.
“But from Surrey’s point of view we’re all hoping he gets out there and scores big runs.”
Pietersen was back at The Oval on Thursday for Surrey’s pre-season press day, posing for team photographs.
The 104-Test veteran’s England career went up in smoke during the disastrous 2013-14 Ashes series in Australia, with accusations and back-biting of dressing room unrest.
Captain Gareth Batty claimed the Surrey dressing room is “even better” with Pietersen around, playing down any chances of the returning star causing any backroom imbalance.
“I can only comment on things I’ve seen with my own eyes,” said Batty.
“But if you go up into that changing room now, Kev will be up there taking the mickey out of someone – and someone will be taking the mickey out of him back.
“It’s a very nice place to be.
“I enjoy coming to work every morning.
“Whether Kev’s there or not it’s a nice place to be, if anything with Kev there it’s even better because there’s a bit more banter, a few more of you boys kicking around and there’s a bit more fun to be had at everybody else’s expense.
“So it’s always been a good place when Kevin’s been around.
“I think he’s very motivated, and I think there’s a bit of fuel there that’s motivating him on a daily basis.
“All I see is a young fella, who is desperate to play cricket, and desperate to get back to his absolute best.”