Dons boss Derek McInnes feels Aberdeen were denied a penalty in the 5-2 defeat by the Scottish Premiership champions.
The Dons appealed in vain when Jonny Hayes was fouled by Efe Ambrose's challenge when they trailed 3-2.
"It's a penalty kick. It's not only a penalty kick, it's last-man for Ambrose and down to 10 men," said McInnes.
"Ultimately, Celtic scored some good goals and had some good performances and have the quality to pick you off."
Celtic took the lead when captain Brown rifled a fine shot past Jamie Langfield, but they were pegged back when Niall McGinn levelled.
Brown netted again before the break and Antony Stokes fired Celtic's third.
And, despite Shaleum Logan netting a ferocious drive, Commons put the result beyond doubt with two late strikes.
And McInnes believes their unsuccessful penalty appeal came at a "pivotal" moment of an entertaining encounter.
"I thought at 3-2 the momentum was with us," he added.
"Effectively, it could be 3-3 playing against 10 men and it's game on. But we never, Celtic got the fourth goal and we were a wee bit open at that stage because you are as well going forward and having a go."
Source: BBC Sport