The arrival of the Norwegian international early in the second half turned the match in Rovers' favour in the 1-1 draw at Turf Moor.
"I think when Josh came on the game changed a little bit," said Berg after the game. "He gave them some problems.
"His link-up play with Kaz and Jordan and with 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."
Rovers are back in action this Friday night when Cardiff City are the visitors to Ewood Park.
Tickets will be on open sale up until kick-off with prices starting from £15 for Adults, £10 for OAPs and £5 for Juniors. Book online today at www.onerovers.co.uk