Whelan featured for Villa in their Championship game against United at Villa Park in the Championship last Friday evening.
The 35-year-old midfielder did not start the match, but the Republic of Ireland international came on as a substitute midway through the second half.
Villa legend McGrath was impressed with the impact that Whelan - who has been on the books of the Villans since the summer of 2017 when he joined from Stoke City for a transfer fee reported by BBC Sport to be worth £1 million - made after coming on, as the Villans staged a dramatic comeback to draw the match 3-3 with United.
Against United at Villa Park last Friday evening, Whelan had a pass accuracy of 89.7% and played one key pass, according to WhoScored.
So far this season, the 35-year-old midfielder made 11 starts and nine substitute appearances in the Championship for Villa, scoring one goal and providing two assists in the process, according to WhoScored.
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