Shackleton started at right-back for Leeds in their 3-0 win over Watford at Elland Road on Saturday.
The versatile player has played in several positions this season and was impressive again before he was replaced by Ayling in the second half.
Ayling has been the regular right-back for Leeds for several years and McCormack stressed that it is to be noted that he has been a consistent performer for the Whites.
The former Leeds captain conceded that Shackleton was good against Watford but does not believe it is time to even consider the notion of him replacing the more experienced right-back in the starting eleven.
McCormack said on BBC Radio Leeds: “[It does] nothing really [to Ayling].
“It’s only one game; it’s important not to get carried away with that.
“Luke Ayling has been doing this for a number of years.
“I read a stat that he has played something around 480 league games in 12 or 14 years.
“He is very reliable.
“He will be happy for Shackleton to go on and produce that performance, but although he was very good today, he has got a long way to go to [for us to] start talking about taking away Luke Ayling’s spot in the team.”
Ayling started seven of Leeds’ eight Championship games and has been the captain in Liam Cooper’s absence.