Former Real Madrid and Everton winger Drenthe made a bright start to his Royals career but has not featured since suffering a foot injury two months ago.
However, Drenthe and fellow summer signing Danny Williams, who also had a foot injury, are back in training and could be available to face Blackburn on November 23.
"The lads who didn't play Saturday were on the pitch having a hard session after the game," Adkins told the club's official website.
"Royston Drenthe was out there, so too Danny Williams. First they need to be training so it's pleasing they're out there, and then build up a level of fitness.
"(Drenthe) has got to get fit, if you want to play football you've got to be fit. He hasn't been on the pitch or trained for eight weeks."