Despite assurances by Chelsea that Duff will stay at Stamford Bridge, he has yet to settle in the capital and Liverpool are confident he would welcome a return to the north-west.
Chelsea have bought the left-sided Dutch international winger Arjen Robben for £12m from PSV Eindhoven and may be more willing to including Duff in the Gerrard deal. Otherwise, Liverpool may increase the price tag to £40m.
