The 20-year old Norwegian striker replaced Morten Gamst Pedersen ten minutes into the second half at Turf Moor and his showing was not lost on Berg who has his services on loan from Manchester United until the end of December.
"I think when Josh came on the game changed a little bit," said Berg. "He gave them some problems.
"His link-up play with Kaz (Colin Kazim-Richards) and Jordan (Rhodes) and with (Danny) Murphy was good as well, we got him on the ball to run at people, to take people on. He also worked hard to win the ball back.
"He is strong, I don't think there are too many defenders who would like to play against him."