With less than 48 hours of the transfer window remaining, the 58-year-old remains frustrated and unhappy due to the lack of funds made available of him - ultimately the reason why he is yet to sign a new contract at St James' Park.
Benitez believes the club have not matched his ambitions, and Lascelles comments suggest he is fully behind his boss.
Lascelles: "I don't know what is holding the cub back"
"We've all got the same drive and ambition," Lascelles told the Daily Mirror.
Benitez guided the Magpies to 10th in the Premier League, and was expected to be given the funds to improve the squad to have them challenging the top eight and a first trophy domestic since 1966.
It is obvious how much the manager means to the players as Lascelles added: "I can't reiterate how important he is.
"Since he has been here - promotion, finishing tenth, everybody loves him, the players love him."
'If Rafa, We Go'
Owner Mike Ashley must back Benitez in the final two days of the transfer window, or see a backlash like no other.
Recent protest campaign groups such as If Rafa Goes, We Go and Ashley Out has called for fans to not renew their season tickets should Benitez leave the club, and Lascelles' comments suggest some of Newcastle's biggest player will follow out the exit door also.
Lascelles impressed last term and has been linked with moves at Everton, West Ham United and Tottenham Hotspur but has stayed put arguably because of loyalties towards Benitez given he handed him the captain's armband at the age of just 22.
And for that, the 24-year-old says "I’d make him the happiest man here if possible".
The Magpies' captain was speaking before the players decided to cut all media connections, even with the club, to protest against the current bonus package being offered by Ashley.
It is believed Ashley is wanting to scrap bonuses for avoiding relegation and winning a cup, however, has offered a cash sum should the Magpies qualify for the Champions League.
This emphasises how different the owner sees the club, compared to the fans, manager and players as frustrations in all corner reaches boiling point.
Ashley doesn't look like he will be changing his stance anytime soon, therefore Benitez must ensure he works closely with his squad and gets every little bit of talent out of them for the season ahead - just like he was required to do last campaign.