The narrow defeat plunged the Magpies back into the relegation zone and piled the pressure back on the team ahead of next weekend's tough encounter with Wolverhampton Wanderers at St James' Park.
Willems said: "It was close. I think we had the game under control and we were a little bit unlucky.
"If it wasn't for the goal I think we did good defensively – they have a good team and they are difficult players to play against.
"Attacking, we could do more.
"In the first half, we could have been more dangerous on the counter attack.
"We had some chances – sometimes we were unlucky, but sometimes I think we need to just shoot when we are in front of goal."