"The current crop are probably under-delivering and one or two of the new ones that have been signed for next season, I'm not entirely sure are going to be an awful lot better," Hargreaves said.
"I just wonder with the consistency, the application, the fitness, the mental stimulation of being over here, are some of those guys making the most of it? I'm not entirely sure.
"You just want quality overseas players that come, give it their best, reflect well on those that play around them, galvanise the crowd and get that right balance for a couple of seasons before they go home or retire."
Savea, who scored 46 tries in 54 tests for the All Blacks, has since responded to damning criticism from the owner of his French rugby club on social media.
"Heading into this week with a positive attitude, whether I am welcomed or not I am still contracted to my team and I will continue to train week in and week out with my brothers #endofstory #letsmoveon," the winger posted.
Savea's brother and fellow All Black, Ardie, retweeted the post in support.
Savea signed a four-year deal with New Zealand Rugby in May 2015 that made him one of the highest paid players in New Zealand history, earning an estimated $800,000 a year. He was released from that deal last year following the Super Rugby season after agreeing on a two-year deal with Toulon.
However, Savea has scored just one try in 10 matches since joining the club. Toulon currently sit 11th on the table with six wins from their opening 16 games.
Former Hurricanes teammate Nehe Milner-Skudder looks set to replace him at Toulon next season having signed a three-year deal.
