Havertz lunged into Lesley Ugochukwu — the Burnley midfielder, not to be confused with the Chelsea player of the same name — catching him down the back of the calf with a studs-up challenge. Tierney gave a yellow card. Bell, the VAR, reviewed the incident and chose not to send Tierney to the pitchside monitor for a second look.
Halsey, who officiated in the Premier League between 1999 and 2013, was unambiguous in his analysis immediately after the final whistle.
"When we look at Law 12 fouls and misconduct, a careless challenge is a free-kick, nothing else. A reckless challenge is a free-kick and a yellow card. And a challenge that endangers the player's safety with excessive force is a red card. Paul Tierney has recognised this challenge by Havertz on the Burnley player as reckless and issued a yellow card.
"But when you look at the challenge, it's a poor challenge. He lunges in, he catches the Burnley player down the back of his calf, high up. A challenge from the front, side or back that endangers the player's safety must be sanctioned as a red card."
He added to The Sun that the failure to act represented another example of the inconsistency that has plagued the officiating of physical challenges throughout the season.
"I was very surprised that VAR did not recommend for Paul Tierney to go and look at the challenge again, because for me it met the criteria in Law 12 misconduct. We've seen on many occasions this season where players have been sent off for those sort of challenges. Something needs to happen regarding the consistency of the officials with challenges, handballs and penalty incidents."
Havertz scored Arsenal's goal in the 36th minute, moving the Gunners five points clear at the top of the Premier League. Arsenal will be confirmed as champions on Tuesday if Manchester City fail to beat Bournemouth.