The big frontman, who has only appeared once in the first team, had been expected to make the step up from reserve team football this year but his injury has put paid to his chances.
Initially, physio Jon Fearn believed that only mild damage had been done and ludicrously predicted that Bas would be back in action in three to four days time.
Fearn told readingfc.co.uk: "Bas ruptured his anterior cruciate ligament at Krumbach a couple of weeks ago. This is incredibly surprising because I thought that he had done cartilage damage.
"With a ligament injury, there is normally a lot more pain, swelling and instability, but Bas didn't have these problems meaning initially I believed he had done cartilage damage.
"The extent of the injury only showed up when we sent the striker in for a scan yesterday. As soon as the camera was inside his knee the severity of the injury was clear.