Koeman left midfielder Sadio Mane out of the starting lineup against Norwich City at the weekend.
Mane started the Premier League game at Carrow Road on Saturday on the substitutes’ bench and came on in the 80th minute.
Southampton lost the encounter 1-0 and now find themselves 13th in the league table, seven points above the relegation zone.
Crooks has criticised Koeman’s decision and has written on BBC Sport: “I'm not entirely convinced that Ronald Koeman's decision to leave out Sadio Mane (arguably his best player) due to lateness for a meeting was his best option.
“Surely hitting the player in his pocket, where it hurts most, would have been much more effective than leaving him out of the team altogether.”
Mane is one of Southampton’s best players, and he was missed against relegation candidates Norwich.
The 23-year-old has scored three goals and created 27 chances in 20 Premier League appearances so far this season.
The former Red Bull Salzburg star has a pass accuracy of 83% and a shot accuracy of 49%, and has won 13 headers, 49 dribbles and 17 tackles.