The Dutch midfielder, who took in a loan spell at Everton in 2011/12, is believed to be flying in to London on Monday to put the finishing touches to a move.
A three-year deal is said to be awaiting the former Real Madrid man at the Madejski Stadium, with his representative revealing on Friday that an agreement was imminent.
Fabian Veldwijk now claims that the paperwork to bring Drenthe back to England could be completed in the next few hours, with the 26-year-old having secured his release from Russian outfit Alania Vladikavkaz.
Veldwijk said: "He's going to England. He is going to sign the contract and hopefully it will be finished tonight.
"Everything is going to happen today. The father is going with him to make sure everything is agreed.
"We have a pretty good feeling that everything will be taken care of. He is really excited about it."