Manchester United opened the scoring in their FA Cup tie against Reading with the aid of VAR after a lengthy delay.
Juan Mata was upended by Omar Richards in the box and Fred slotted home from the loose ball, but the Brazilian's effort was ruled out for offside.
However, after a considerable stoppage as the referee deliberated, the goal was disallowed and a penalty was awarded for the foul on Mata.
The Spaniard dusted himself down to take the spot-kick and dispatched it coolly, sending it into the bottom-right corner, with Anssi Jaakkola diving the wrong way.
The midfielder has now been directly involved in 21 goals (10 goals, 11 assists) in the competition from just 24 starts.
Romelu Lukaku and Alexis Sanchez are making their first starts since Ole Gunnar Solskjaer took over from Jose Mourinho, with the pair linking up to double United's lead just before half-time.
The Belgian got in behind the Royals defence to latch onto Sanchez's pass and rounded the goalkeeper before slotting into an empty net from a tight angle.
The pair will be pleased to have been involved in a goal as they both look to make a claim for a regular starting berth, with Marcus Rashford, Anthony Martial and Jesse Lingard featuring regularly under the Norwegian.
Lukaku had been on compassionate leave for Solskjaer's first two games, while Sanchez has recently recovered from injury.
The two strikes also represent the 15th and 16th goals of the caretaker manager's four-and-a-half game tenure, with United having scored 14 in their previous nine.
United faced Reading in the same round of this competition two years ago when the Red Devils emerged as 4-0 winners.
Elsewhere in FA Cup action, VAR was brought into use as Burnley were awarded their first penalty in 18 months against Barnsley, only to see the decision ruled out.