Arsenal manager Arsene Wenger has questioned whether Anthony Martial will "strengthen" Manchester United following his £36m switch to Old Trafford.
The Red Devils sealed the signing of 19-year-old Martial from Monaco on transfer deadline day earlier this week.
Wenger believes that United's willingness to spend a hefty amount on a relatively unknown player proves that there is a lack of quality available to the top clubs.
"The problem at the moment is finding the players that guarantee you are a better team," Wenger told beIN Sports.
"What happened with Monaco, who sold Martial to Manchester United for €80m - Martial scored 11 goals in the French championship - that sums it up well.
"That means it's not the money that's missing at the moment, it's not the desire of investment that is missing, it's the number of players available who can strengthen the big clubs."
United spent more than £100m on players in the summer transfer window, while Arsenal parted with just £11m to buy goalkeeper Petr Cech from Chelsea.
