The phrase "to press the opponent" means to apply constant pressure and attack aggressively in order to put the opponent on the defensive and limit their ability to act or respond effectively. Full definition
They don't control the game particularly well for a team at this level — just 55 percent possession — and they don't press opponents when they lose the ball. (theringer.com)
He expects his players to play like they are going into battle and to press the opponents off the ball. (caughtoffside.com)
Was kicking goals, pressing opponents back lines, slide - tackles. (justarsenal.com)