England's Ben Stokes will have an MRI scan on a calf injury on Tuesday after leaving the field during the 330-run win over Pakistan in the second Test.
The all-rounder pulled up in his follow-through in his sixth over on the fourth afternoon at Old Trafford.
Stokes, 25, was making his return to the England side after missing three Tests following knee surgery.
Pakistan, set 565 to win, were bowled out for 234 as England levelled the series 1-1.
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Former England captain Michael Vaughan said on BBC Test Match Special: "He looks like he has done some real damage to that calf. He will be missed."
Ex-England spinner Vic Marks said: "This is a worry - he stopped so abruptly. When people go off straight away like he did, you can sense it's serious."
The third Test of the four-match series starts on 3 August at Edgbaston, with the final Test at The Oval beginning on 11 August.