Manchester United are struggling to sell several first-team players this summer.
United fans are becoming increasingly restless as the club have only signed Donny van de Beek so far in the summer transfer window.
And according to Sky Sports reporter Dharmesh Sheth, the lack of arrivals is due to United's inability to cull their squad.
"Departures are proving very, very difficult for United and there seems to be a feeling of surprise at Old Trafford that they are unable to get suitable offers for some of their players," Sheth told Sky Sports News' The Transfer Show.
"For example, Chris Smalling is still training on his own away from the first team, but Roma are yet to meet United's valuation. By all accounts United want to do business with Roma, who want to do business with United, Smalling was on loan there last season, had a successful spell there and wants to go back.
"All those elements are in place except the one most important element, the fee. It simply cannot be agreed at the moment."