The phrase "strong tackler" refers to a player in sports, usually football or rugby, who is good at stopping opponents by forcefully bringing them down to the ground. Full definition
Kos on the other hand, has a very good pace, really quick reaction, strong tackler as well. (justarsenal.com)
I hope the rumour about Rabiot coming to fruitful, I like the physique of the guy, tall and strong, very comfortable on the ball as well, strong tackler. (justarsenal.com)
He is a strong tackler and has great instincts. (justarsenal.com)