"It's obvious there are younger riders who are faster than him," Lorenzo told Spanish media.
"It must be frustrating not to have the speed that would have allowed him to win more races and arrive in Valencia with a greater advantage," added the 28-year-old who won seven races to Rossi's four.
"We don't know what will happen in the future but probably, just as will happen to me, this was his last chance to be world champion."
New MotoGP world champion Jorge Lorenzo has accused Yamaha team mate Valentino Rossi of sour grapes after Sunday's deciding race in Valencia, saying the Italian knows he will never win another title.
Rossi boasts the longest winning career in grand prix history with a span of 19 years between his first triumph in 1996 in the 125cc category and his most recent MotoGP victory in August.
Next February he will be 37, the same age as the oldest champion ever in the top category -- Britain's Leslie Graham who won the inaugural 500cc championship of 1949 after a career interrupted by wartime.
Rossi has said he will race on next season but 2015 may well prove to have been the final flourish of a man who ranks as the greatest rider of the modern era with nine world championships including seven in the premier class.
Only compatriot Giacomo Agostini, who raced from 1964 to 1977, has won more.
Rossi showed his class on Sunday when he carved through the field from last place to fourth but was unable to get close to the leading three Spaniards -- Lorenzo and Honda riders Marc Marquez and Dani Pedrosa.
He later accused the trio of a cosy agreement to stitch up the result and ensure one Spaniard handed over the title to another, and did not attend the prize-giving gala evening.
Outgoing champion Marquez, already a double MotoGP title winner at the age of 22, was there and represents the future.
The Spaniard has become Rossi's arch-enemy, with the two clashing on a number of occasions and the Italian accusing the Honda rider of helping Lorenzo and acting like his 'bodyguard'.
Rossi was sent to the back of the grid in Valencia after tangling with Marquez at the previous race in Malaysia with the Spaniard crashing and accusing the Italian of kicking him off his bike.
Lorenzo, who was whistled on the podium by the sizeable contingent of Rossi supporters in the Valencia crowd, suggested the bad blood had an easy explanation.
"None of this controversy and comments would have happened if Valentino had the speed of Marc, of myself, and had won more races," he said.
"With a bit more speed and consistency, and without what happened at Sepang, he could have arrived in Valencia with a clear advantage and won the championship comfortably.
"It was not like that and he knows that he let slip this year the opportunity to win his 10th championship and that is hard to accept."
