Spurs remain rooted in the bottom three with only one Premier League win all season after a 3-1 defeat at St James' Park which piled further pressure on the manager.
The defeat ended Spurs' unbeaten six-game run and left Jol facing fresh criticism, although he remained unbowed.
He said: "If everybody comes back, we have got a very good team and a very good defence.
"We still lack a bit of leadership, but it is about mental strength as well.
"Two years ago, we had that; last year at the start of the season, we lacked it as well, but we came back.
"Even today, we tried to come back, but we concede goals at the wrong moment all the time."