The in-form England international - our Player of the Month for both February and March - was enjoying another fine performance as Ole Gunnar Solskjaer's men kept out the hosts and moved into the lead in our Europa League tie, with an excellent strike from Marcus Rashford.
But Shaw, who was booked two minutes before the break for a foul on Antonio Puertas, did not return to the field when the second half began. Brazilian defender Alex Telles came on in his place at left-back.
When asked in his post-match press conference whether his decision to withdraw Shaw from the fray was tactical or due to an injury, Solskjaer indicated it was a precautionary measure.