The Red Devils are looking to record a fifth successive win at The Hawthorns after an impressive run for Louis van Gaal’s side over the past 11 days.
The 20-time English champions have beaten Shrewsbury Town, FC Midtjylland, Arsenal and Watford in their last four outings in all competitions.
Mata was United’s hero on Wednesday night after the Spain international netted a brilliant free-kick in the final seven minutes to seal three points.
And the club’s second-most expensive signing of all-time took an impressive picture of United’s snow-covered Carrington training ground on Friday morning.
Mata wrote: “Good morning.”
The Red Devils are in fifth place in the Premier League table and level on points with Manchester City, who occupy the final Champions League qualifying spot.
United are in action against West Brom in Sunday’s late kick-off.
MORE: The latest football news