Karlovic took command from the start, smashing seven aces in his first two service games and making an early break. The Croat went on to close the match with his 22nd ace.
"Yeah, it was frustrating, to say the least," Hewitt said. "It doesn't give you a chance to do a lot of things. You can't assess where you're at at the moment. You know, I can't assess my movement. Yeah, so it's just a frustrating day, all up."
Hewitt, a four time winner of this tournament, failed to earn a break point in his eighth match of the season. The Australian was once ranked No. 1, but he has slumped to 205th following injuries. He needed a wild card to compete in this Wimbledon tuneup.