#4 Radamel Falcao loans to Manchester United and Chelsea, 2014-2016
Radamel Falcao was at one point considered one of the greatest strikers in European football. Aside from his time in England, Falcao scored goals on a regular basis.
The Colombian scored 41 goals in 51 league games for Porto, 52 goals in 68 league games for Atletico Madrid and 32 goals in 49 league games for Monaco, which are some outstanding goal returns.
At Chelsea and Manchester United, in a combined 36 Premier League appearances, he scored just 5 goals, an atrocious record for a proven goal scorer. As time went on, his confidence plummeted. Quite possibly the reason for his failures at Chelsea and United were that he was playing in negative teams under both Louis Van Gaal and Jose Mourinho.
Injury plagued most of his second loan spell at Chelsea but one goal in 10 games suggested he was still low on confidence. He has since returned to Monaco and thrived in a young and vibrant side, implying he just wasn't cut out to play in the Premier League.