Law 12:
A direct free kick is awarded to the opposing team if a player commits any of the following seven offences in a manner considered by the referee to be careless, reckless or using excessive force:
- kicks or attempts to kick an opponent
- trips or attempts to trip an opponent
- jumps at an opponent
- charges an opponent
- strikes or attempts to strike an opponent
- pushes an opponent
- tackles an opponent
“Careless” means that the player has shown a lack of attention or consideration when making a challenge or that he acted without precaution.
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So in asking whether this is a penalty, the only question is this:
Did Player A kick/trip/tackle an opponent with a lack of attention or consideration when making a challenge, or without precaution.
Yes: pen.
No: play on.
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Now, kick and trip require contact by definition. You can't kick someone without kicking them.
Tackling however, not so much. You can make a tackle without contacting an opponent. It can still be a penalty. (Crazy imho, but that's what the rules say).
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I initially thought the pen today was a Greek dive. But the replay showed a trip. So I'm comfy it was a penalty.