Former Cardiff City striker Earnshaw's five goals are second-best in the league.
"You miss a pass or you miss something or you let the ball bounce and you don't attack it before him, he will punish you. That's what he does best,'' Arsenal legend Henry told the New York Post. "I've played against him, I saw him play so many times.
"He's the type of striker that you might not see him a lot in the game but at the end you might see his name quite often on the scoresheet. We have to be careful. Good player. Good striker. Hopefully he's going to be able to score goals, but not against us."
NYRB teammate Tim Cahill seconded their need to be wary of Earnshaw.
"I know him personally,'' said Cahill. "I know what he's done in the Championship and during his time in the Premiership, as well. He's a very good footballer with a good footballing brain. But in and around the area, half-a-yard snapshots, he's really trying to catch the 'keeper flat-footed and slot them to the bottom corners, but also an opportunist."