Sanchez said: "'Joe' offers us something unique. He has fantastic pace, he has scored two goals, and he should probably have had a couple more.
"If he starts, he is different, and he causes teams problems. As a substitute, he does create havoc when people are tiring, and he should have won the game for us at Chelsea last weekend (when Fulham drew 0-0).
"Joe has proven that he is a good enough player for the Premier League. When he was at Portsmouth last time, he was just getting a taste for it.
"I think Harry Redknapp signed him, and then he was replaced, so perhaps things didn't work out for Joe as much as he would have liked, but I am very pleased with him.
"Does he have something to prove to Portsmouth? You would have to ask Joe that, but I don't think he has anything to prove."
"The facts are that he went to West Brom, scored a lot of goals and got himself back up to the Premier League."
Sanchez fought off competition from other top-flight clubs to sign Kamara, who scored 23 times for West Brom in the Coca-Cola Championship last season.
Portsmouth expressed an interest in their former player, but Kamara, 26, opted to move to Craven Cottage.
That he did so is proof that Fulham can become a major player in the Premier League, according to Sanchez.
"Fulham is a decent club. We compete in the Premier League with other clubs from a financial point of view.
"It is a decent place to live, there are good working facilities, so it is an attractive club to come to.
"It does not surprise me that players want to come here."