Red Devils boss Jose Mourinho has used the Spain international sparingly in the 2017-18 season so far.
Mata was an 82nd-minute substitute in Manchester United’s 2-1 loss to Manchester City in the derby at Old Trafford last weekend.
The World Cup winner was handed a starting spot for the visit of Bournemouth on Wednesday night as Mourinho looked to spice up his line-up.
And the 29-year-old repaid Mourinho with a brilliant assist to tee up Romelu Lukaku to score a first-half winner in a 1-0 victory over Bournemouth.
Mata has scored one goal and has made three assists in 17 appearances in all competitions in the 2017-178 season so far.
Former Liverpool midfielder Murphy questioned why Mata hasn’t been given more of a chance to prove a creative force in Mourinho’s midfield.
“It was a great ball from Juan Mata,” Murphy told BBC Sport. “I am surprised he hasn’t played more.”
Mata moved to Manchester United in a £37m deal from Chelsea in January 2013.
The Spanish midfielder has won the Europa League, the FA Cup and the League Cup since his move to Old Trafford.
The Red Devils finished in sixth place in the Premier League table last season.
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