Prior to Torres's £50m arrival last year, the 35-year-old Ukrainian was the Pensioners' club-record signing following his £30.8m move from AC Milan.
Shevchenko struggled in England, managing only nine Premier League goals before eventually leaving on a free transfer to current club Dynamo Kiev. However, he is confident that Torres will do better.
"I think Torres has played well and is trying hard. He is unlucky not to be scoring goals and I watch him many, many games," said Shevchenko.
"He is moving a lot, doing a lot of work for the team and I think Torres needs time. His physical performance is good, he is just unlucky not to be scoring.
"They have changed the manager and everything, which is not helping. Football is only about the opportunity. If you trust yourself, an opportunity comes and you score an important goal it can change your story with the club."
Torres has scored three goals in 27 Premier League appearances this season.