England's May 'all-in' for World Cup with Test retirement on horizon
May was then omitted from the World Cup set-up in August, before being handed his chance as a replacement for the injured Anthony Watson weeks before the tournament began.
On Saturday, the 33-year-old will start against Samoa in England's final group game with Borthwick's side already guaranteed a spot in the quarter-finals.
"This will be definitely my last World Cup, most likely my last time playing for England, at this World Cup," May told reporters on Friday.
"Never say never but probably, most likely, this will be the last campaign I'll have with England.
"And I'm incredibly grateful to be here.
"And I told Steve, in January, I'm all in, and that's the sort of guy I am," the Gloucester player added.
England, World Cup winners in 2003, are set to face Fiji or Wales in next weekend's last eight.
It is now a little more than a decade since May made the first of his 75 Test appearances.
"There will be relief when this comes to an end. As much as it is a blessing to play for your country it also is a weight you carry," May said.
"You carry it with your club, at Christmas, you think 'I've got to be on it, I've got to be on it' and that's what drives me.
"But there will be relief with knowing I've done the best I can when club and international rugby comes to an end," he added.
'At peace'
May is second on England's top try-scoring list behind Rory Underwood.
Despite the personal accolades and team achievements like a World Cup final four years ago one thing is missing from his rugby CV.
"A big goal of mine was the 2021 British and Irish Lions tour," May said
"That didn't work out for me, that was a bit tough.
"I'm at peace with that now, and happy to talk about it.
"Beyond that Lions tour, anything internationally I saw as bonus time," he added.
This weekend May will feature outside a familiar playmaking trio.
Borthwick has selected George Ford at fly-half, Owen Farrell at inside centre and Manu Tuilagi in the No. 13 shirt to face Samoa in Lille.
"These guys I've played with a lot, an 11-year period," May said.
"I'm as close to these guys, closer than I am and have been with any club partnership I've been a part of.
"Having access to those guys, what they've shared with me, and the way I've been able to learn from them, I just feel so grateful to have been so lucky."
