The Indian quick picked up a thigh injury towards the end of the Royal London Cup campaign and went home for further assessment, but he will not be available for the final matches of the season
Umesh Yadav will not be returning to Middlesex for the climax to the LV= Insurance County Championship season.
A quad injury picked up during the Royal London Cup clash with Gloucestershire led to him returning to India for further assessment.
The BCCI have since concluded that the injury remains "a cause for concern" and he will not be released back to the Lord's club for the final two red-ball matches.
Yadav had initially been signed up as a replacement for Shaheen Shah Afridi, whose spell was cut short due to his participation in Pakistan's Test series in Sri Lanka.
He played three County Championship matches against Worcestershire, Sussex and Durham ahead of the Royal London Cup, during which he took 15 wickets.
But it was towards the end of that campaign - the five-wicket defeat by Gloucestershire - that injury struck, forcing him to return home and miss the final match against Sussex at Hove.

Yadav picked up 15 wickets in the Royal London Cup (Stu Forster/Getty Images)
That absence extended to this week's Championship visit of Glamorgan, but Middlesex were hopeful he would be available for the last two matches, starting against Leicestershire from September 20.
"We are naturally disappointed that Umesh will not be returning to the club for the final two matches of the season, however throughout his recovery process we have been in close contact with the BCCI's medical team, and completely agree with their assessment that a precautionary approach to his return to action is sensible," head of men's performance cricket Alan Coleman.
"Umesh fit in brilliantly to the squad when he joined us earlier this year and played with great passion and commitment throughout his time with us.
"He gave 100 per cent at all times and completely bought into everything we are trying to achieve as a squad."