Andrews saw the Bees defeated 3-1 on his management debut, with Igor Thiago scoring the visitors' goal.
Afterwards, Andrews said: "It was a really disappointing first half and a really disappointing result," said Andrews.
"It got away from us in the first half at stages and they were clinical, which we knew they would be.
"We were a little nice at times, and I didn't like it.
"It's easy to say in the second half to show what you're about and show some personality, but it's not always easy to implement it on the pitch. I was really happy with what the players showed in the second half."
On the absence of Ethan Pinnock, Andrews added: "Ethan just picked up a knock in training, it was pretty innocuous really.
"It's nothing major, I don't think. He's being treated back at the training ground and hopefully will be available pretty soon."