The defender put pen to paper on a new six-year deal with the Premier League outfit on Thursday, despite the turmoil the club is currently in.
They sit second bottom of the league table, and have still not been able to get a competitive win this campaign.
Added to this, the Benitez's contract is due to end at the end of the season, with no solution in sight, but Lascelles insists the club remain focused on the short-term goal of earning three points every weekend.
"I don't really sense that [the squad are unsettled]. All I sense is we're a group of players, this is what we've got, this is the manager we've got, this is the owner we've got, we've got to get on with it. We need to get on with it as players.
"Me personally, as long as he [Benitez] is here, Newcastle will keep going up and up. Having worked under him, to be honest I didn't know there was uncertainty about him not being here."