Souness has brought in Steven Reid for £2.7 million from Division One side Millwall, but England international Jansen will battle for inclusion.
"Duffer has gone and if there is a place there I want to take it. It's a new position for me and it's one I'm willing to learn," said Jansen.
"I need games to get my confidence back and I am happy to play on the left.
"The manager hasn't said anything. He has just asked me to play there. He said at the moment he just wants me to get fit."
Meanwhile, Reid has insisted that his man-of-the-match start to his Ewood Park career should not bring comparisons to Duff.
"Damien Duff will be irreplaceable. It would be impossible to replace someone as good as him and I'm not going to be able to do that," said Reid.
"He is one of the best left-sided players in Europe, so it would be hard for me to even match him.
"I just want to get my head down and get on with helping Blackburn to do well."
