Jose Mourinho was warned about signing Romelu Lukaku for Manchester United. Lukaku arrived at Old Trafford in a £75m deal from Everton in 2017 but left just two years later for Inter Milan.
After a decent start to his United career, Lukaku's form dipped and he found himself out of the plans of boss Ole Gunnar Solskjaer. Mourinho was the man to bring the Belgian in, having worked with him at Chelsea before he left for Everton.