Derby County boss Wayne Rooney has accused Crystal Palace and other clubs of taking advantage of the Rams' financial situation in the January transfer window.
The Eagles plucked teenage striker Luke Plange from Pride Park on deadline day for a reported fee of £1million but have sent him back on loan to the club for the remainder of the season.
Derby also lost 18-year-old left-back Dylan Williams to Premier League side Chelsea, who had only made nine first-team appearances for the club before departing this month, and lost experienced full-back Graeme Shinnie to Wigan.
"Some people might look at it and say, it's young players that (have) gone out, but we've been relying on young players all season, so it's a big hit for us," Rooney told BBC Radio Derby via Express.
"We're in a difficult position and I feel other clubs have taken advantage of that. Whether that's Wigan with Graeme Shinnie, Crystal Palace with Luke Plange, they've seen an opportunity.
"There's a reason why they've come in and tried to do it now because they know they are getting the players a lot lower than they are actually valued at."
Crystal Palace were applauded by some Derby fans for the message that Steve Parish sent to the club following the deal to sign Plange on deadline day.
The chairman and co-owner described the deal as mutually beneficial for both clubs and offered his support to the Rams in their plight for survival.
"[Luke] has an important role to fulfil playing at Derby, and we appreciate his significance to them in their current circumstances," he said.
"It is less than 12 years ago that our club was in a similar situation - as a result, we were determined to ensure both clubs benefit through this deal. Therefore Luke will return on loan for the remainder of the season and help Derby with their important battles on and off the pitch."
