The Colombian endured a difficult season at Manchester United but is now gearing up for the 2015-16 campaign with Chelsea and Crespo believes that it will not be easy for himHernan Crespo says that Radamel Falcao was "the best of the human players" before his knee injury, warning him that he could continue to struggle at Chelsea.
Falcao has moved to Stamford Bridge on a one-year loan deal from Monaco, after enduring a frustrating 2014-15 campaign with Manchester United that yielded just four goals and questions about his top-level ability.
The Colombia striker damaged the anterior cruciate ligament in his left knee in January 2014, which ruled him out of the World Cup, and he has since struggled to recapture the form which made him one of Europe's most feared forwards during his time with Porto and Atletico Madrid.
Crespo, who himself moved to the Blues in 2003 but was loaned out to both Milan clubs by Jose Mourinho during a difficult five-year spell in England, says that Falcao is now a different proposition.
"There is a big difference between Falcao before and after his injury," Crespo, now coach of Italian Serie B side Modena, told the BBC.
"Before the injury, he was the best of the 'human players' - all players apart from Lionel Messi and Cristiano Ronaldo, who are on another level.
"After such an injury, you need time and it's not easy to recover. It won't be easy for him. Jose doesn't give presents away."
However, the former Argentina hitman insists that a little bit of belief would be enough for Falcao to convince his new manager, something which he was unable to do with Louis van Gaal at Old Trafford.
"All Falcao has to do is to believe in himself and be the great player he is," Crespo added. "That will be enough to convince Mourinho to give him a chance. He was probably not the kind of player Van Gaal was looking for.
"You have to take your chances if you want to play regularly. We will see what happens at Chelsea."