On the one hand If you take it that there are 22 men on the pitch then over a 90 minute game they will each have the ball for approximately four minutes each. As you know the ball is not in play for 90 minutes and, from stats I recall recently, the ball is only in play about 60 minutes per game. With that being the case the average time each player is in possession is now under three minutes a game.
As Clarke came on for the last 10 minute plus injury time then he was on the field for about one sixth of the match. That means he would have been in possession of the ball for about 30 seconds. In that time he did what you say, including scoring a goal.
On the other hand I am not anally retentive and saw a decent football game between two well matched sides. They had the better of the first half and we had the better of the second. There was a good penalty shout, four well taken goals, a goal mouth melee, a fine goal celebration from Billy and a row between the managers. I call that entertainment. You need to sit down and look at yourself before posting.