Arsenal boss Arsene Wenger says fans must understand how difficult it is to work the transfer market.
January was one of the busiest transfer windows in Wenger's career.
High-earning squad players also left, most notably Francis Coquelin and Mathieu Debuchy, but Wenger has admitted he was unable to complete all the business he wanted to.
A £12m bid for Jonny Evans was rejected by West Brom but Wenger insisted the process of rebuilding his squad mid-season was even more complex than it appeared.
“I must say as well people don't realise how much work is behind these transfers," he added. “How much uncertainty, how much energy, how much travelling, how much sleepless nights is behind that and it's difficult to combine all that together and to make it all work you know?
“It's so difficult. I made over 300 transfers in my Arsenal career but they're always longer now, more detailed, more uncertain and you need more people to work around it.
“It's not as easy as you know you come in and you give £10 & you buy something you know? It is a long process and a lot of work."