A BBC television investigation into the death of Bob Woolmer, shown on Monday night, claimed that toxicology tests support earlier reports that he was poisoned before being strangled.
The Panorama programme said that there is evidence of a drug being present in his system that would have incapacitated him.
"It now seems certain that as he was being strangled, he'd already been rendered helpless, leaving him unable to fight back," said Adam Parsons, the show's producer. "The specific details of that poison are now very likely to offer a significant lead to finding his murderer."
Parsons' programme also claimed that while Woolmer had a good relationship with his players, there were deep religious divides inside the Pakistan team and that Woolmer was growing increasingly frustrated with the effect this was having on the side.
An example given was that players left the field to be replaced by substitutes to enable them to pray during matches. "He was totally against it," said Pervez Mir, Pakistan's media manager. "He felt he shouldn't really be subjected to it. I agreed with him."
Mir also said that there were players who preferred to "pray not play", and he revealed that his comments had led to him receiving death threats on his return home.