Campbell, who turns eighteen on Friday, will spend the next two weeks at Celtic on a work experience based loan deal.
The youngster, who was born in Scotland, previously enjoyed a similar loan spell under the watchful eye of Sir Alex Ferguson at Manchester United.
Despite having made just one substitute appearance for the Royals, Campbell's potential is such that he is being courted by Europe's finest.
The winger was expected to make a big impression on the team this season having put in some top reserve team performances last year, which culminated in his first appearance in the first team.
However, academy chief Brendan Rodgers revealed that Campbell has failed to impress this year, yet he is hoping the young Scot can recapture the spark that so nearly ignited his Reading career a year ago.
"It's been a difficult year for Darren," said Rodgers, speaking to the official site.
"He was successful last year when he played for the first team, some of his potential was realised.
"This year he has struggled with the physical aspects of the senior game. He's gone up there (to Celtic) to give himself every chance of regaining some of that hunger and it will be a change of environment for him."
*Campbell made his first team debut when came on as a seventy-ninth minute substitute for Nathan Tyson during our end of season clash with Watford at Vicarage Road last season.