The 'human error' that may cost Arsenal the English Premier League championship

The English Premier League has long been decided by the smallest of margins; a point here, a goal there.

A single point separated last year's champion Manchester City from runner-up Liverpool, and as Jurgen Klopp's side is learning, chances to win the title do not come around often when you are languishing in the middle of the table.

So when "human error," as admitted by the body in charge of Premier League referees, allowed Brentford's equalizer to stand in a 1-1 draw with league leader Arsenal, it elicited a rage as it denied the Gunners a crucial victory.

"I just looked back and it is offside, yes," manager Mikel Arteta said later on Sky Sports. "Did they explain why it wasn't permitted? No. It's frustrating, but they'll get there.

Ivan Toney headed in a goal with Brentford trailing 1-0 after the ball bobbled around the penalty box from a free kick.

Lee Mason, the Video Assistant Referee (VAR), checked Ethan Pinnock's challenge on Gabriel during the initial free-kick but did not appear to use the VAR guidelines to check a second incident in the goal's buildup when Christian Norgaard appeared to be offside.

"When defending, you must adhere to certain principles, which you do by following the rules. "Suddenly, the rules change, and you have to change your principles," Arteta continued.

"So tell us ahead of time so you don't hold the (defensive) line that high. Because you will always have an advantage if you are blocked. Offside means you can't block."

The body in charge of Premier League referees, Professional Game Match Officials Limited (PGMOL), told CNN that its Chief Refereeing Officer Howard Webb had contacted Arsenal "to acknowledge and explain the significant errors in the VAR process."

It went on to say that the error was being "thoroughly reviewed by PGMOL."

Arsenal's draw against Brentford marked the second consecutive week in which it dropped points after a shock loss to Everton, and its lead over Manchester City is now only six points, rather than eight if it had won against Brentford.

The Gunners will play City on Wednesday in a game that will most likely define their season.