Red Devils manager Louis van Gaal started the pair up front alongside Danny Welbeck for United’s goalless draw with Inter Milan on Tuesday.
The 20-time English champions went on to claim victory after a 5-3 penalty shootout triumph, marking Van Gaal’s third successive win.
And Mata, who moved to United in a £37.1m deal from Chelsea in January, tweeted the mistake to his 3.91m followers.
In what was a poor night for United’s in-house broadcaster who made a total of nine mistakes; Luke Shaw, Ander Herrera, Darren Fletcher, Jonny Evans, Phil Jones and Rafael da Silva were also mistakenly identified.
Mata scored six goals and made four assists in 15 Premier League appearances following his move to Old Trafford.
MORE: Man United latest news
MORE: Arsenal latest news
MORE: Chelsea latest news
MORE: Liverpool latest news