Referee

Jack wasn’t one for playing football. He much preferred watching it.
Henry and Jim though, they played for the youth academy of the local team, Picksbridge FC. As Jack stood on the sidelines for their big match against their rivals, Agsford FC, he spotted Jim moving over.
“You may as well leave now.” Jim said gloomily. “They’re canceling the match. The referee’s sick.”
As Jim said, one of the coaches held up a megaphone and called:
“The game is canceled due to the lack of a referee.”
There was a resounding groan all over the ground. Jack saw a man lumbering up to the coach. Probably a complaining dad, he thought. Jack didn’t recognise him, though, which meant he was one of the Agsford fathers.. He was a fairly sturdy man with an unusually black T-shirt and shorts with one front pocket in his shirt and one in his back left.
After the man had finished talking to the coach, the coach nodded and put up his megaphone and announced:
“The game has not been canceled as we have a former Championship referee with us. He will be refereeing the game.”
The crowd relaxed and the game soon began.
From the start, it was clear to Jack that Picksbridge FC were vastly superior to Agsford FC.
In the first ten minutes, Jim was through on goal in the penalty area, and the goalkeeper had rushed out. Jack held his breath as Jim pulled back his leg and…
A defender slid into the back of him with such ferocity that a saber-toothed tiger on steroids would’ve been scared. Jim fell to the ground, clutching his right leg, which had been affected by the tackle. Jack thought, Oh well, at least a penalty would be given. And that defender will probably be sent off. But it was to his surprise that the referee didn’t give Jim a penalty and even gave him a yellow card, reaching out of his shirt’s front pocket to give Jim a yellow card for diving.
In the next thirty-five minutes, Jack became certain that the referee was biased towards Agsford. Nevertheless, he cheered with all his might. The crowd watched and Jim won the ball back cleanly, but the opponent started writhing on the ground. The referee walked over.
The crowd gasped.
The referee reached for his front pocket held up a second yellow card. Jack’s heart sank as the referee brandished a red card up high after reaching for it in his front pocket. Then he whistled his whistle for half-time. Jack walked over to Picksbridge FC’s dugout where the the team sat looking glum.
Jack called at them.
“Don’t be down, Jim. The referee is biased against the other team.”
“I know,” said Jim, looking glum. “But we can’t prove it!”
“Yes we can.” said Jack.
Why?