If he is alone with the puck close to the goal, he has a good chance of whacking it in. Offense is about finding empty ice. Every child starting in hockey learns this right away. The puck is advanced by carrying it or passing it through open ice. If there is lots of open ice, the players fill it and the puck will be shuttled toward the goal at a lightning pace.
Defense is about finding empty ice and filling it first.
It is not about checking, not really. It is about beating the attacker to the empty ice. It is about denying the offensive player the time to take a good shot or make a good pass. Denying the ice forces a turnover. There is a balance between offense and defense in this battle for territory, but the scales slightly favour the defense.