ID for this wader. (only this shot)
Mudflats, Karachi coast, Sindh, Pakistan
Can it be a Red knot?
Size: Larger than a Dunlin, also the bill and head shape is different (observed on spot)
Grey upperparts, diffused grey chest collar (from this shot), faint streaks ,thick, straight, not so long bill, Straight white supercilia
Birds out of option: (in my opinion)
Curlew sandpiper (has a different bill shape, etc )
Little stint (size, color, etc)
Dunlin (bill shape and length, size, etc)
Sanderling (Size, color of upperparts, etc)
Also Broad billed sandpiper, Sharp tailed sandpiper, other sandpiper species.
This shot is crop from this image. This individual (left fore front) was mixed in a flock of over 2000+ small wader flock including little stints, Curlew sandpipers, Greater and lesser sand plover, etc.