Is it really harder to play against 10 men?
"It's always difficult to play 11 against 10 away from home," said Arsenal manager Arsene Wenger last month after his team beat Newcastle United 1-0. But managers and pundits often go further, saying "it's harder to play against 10 men". Can this really be true?
The thought is that a team with 10 men retreats back and focuses on defending its goal, making it harder for the team with an extra man to win.
Although Newcastle lost after Aleksandar Mitrovic's 16th-minute dismissal, some teams have famously triumphed with 10 men.
One notable example was Chelsea's dramatic win in the 2012 Champions League semi-final, despite having captain John Terry sent off in the 37th minute of the second leg, playing away against all-conquering Barcelona.
But this is the exception rather than the rule, according to new research carried out by Adam Greenberg, a recent graduate of economics and econometrics at the University of Nottingham, whose study of 1,520 Premier League matches between 2009 and 2013 was first published in Significance magazine.
He found that a team scores significantly fewer goals and gets fewer points after having a player sent off.
"The research shows that the difference in points between a team playing with 11 men and 10 men is maybe as much as half a point on average," he says.
Greenberg's research was the first of its kind to focus on the English Premier League, where three points are awarded for a win and one for a draw. Other studies focusing on international football have also found no basis for the red card cliche.
But Greenberg also found that the effect of having a man sent off differed, depending on whether the team was playing at home or away.
"The home team will actually suffer a lot more from having a player sent off than they would gain if the away team had a player sent off," Greenberg says "It's actually over twice as big an effect."
Home teams won an average of 1.69 points per game across the four seasons Greenberg analysed when a match was 11 versus 11.
When the away team went down to 10 men, home teams won an average of 2.05 points per game - a difference of 0.36 points.
However, when the home team had a player sent off the average number of points they won was 0.83 - a difference of 0.86 points.
Greenberg thinks a home team suffers badly when it has a player sent off because the pressure not to lose in front of its own fans is so great.
The away team, on the other hand, is not expected to win - so when it gains an extra player it is emboldened to attack and try to win the game.
The position of the player a home team has sent off also makes a difference. Having a defender sent off resulted in an average loss of about 1 point, while an attacker resulted in an average loss of about 0.9 points. Most dispensable were midfielders - when they got a red card, the average loss was only 0.6 points.
So next time you hear the cliche that it's harder to play against 10 men, bear in mind that it's not actually true.
Greenberg has now set his sights on two other well-worn phrases: "Two-nil is the most dangerous score line in football," and "You are more vulnerable when you've just scored."
More or Less is broadcast on BBC Radio 4 and the World Service
Subscribe to the BBC News Magazine's email newsletter to get articles sent to your inbox.