Pakistan may have to make do without the services of spin-bowler Yasir Shah for their first Test match against England, which gets underway in the United Arab Emirates tomorrow morning.
The 29-year-old suffered a "back spasm" during today's net session, which captain Misbah ul-Haq conceded has left the selectors "really concerned".
"We're hoping he'll be fine, but obviously he's a key player for us, so we're really concerned about it," Ul-Haq told reporters.
"It's a back spasm, I think. He just tried to bowl a delivery and his spikes stuck [in the turf]. He felt something in his back. Let's see how he feels overnight."
News of Shah's potential unavailability has come on the same day that England bowler Steven Finn was ruled out with a foot problem.