After a seven-match unbeaten run came to an end with a 1-0 defeat at Udinese, Ventura was furious with a Toro side who did not get going in the first half.
The Granata finally sprang into life after the break but could not muster a response to Roberto Pereyra's early goal.
Atalanta have suffered from similar inconsistency this season and Ventura wants Torino to show more willing than their opponents across 90 minutes.
The veteran coach said: "That match showed us exactly what kind of team we must not be and what kind of team we can be.
"We had a quitter's attitude in the first half and only in the second half did we start to put some pressure on Udinese, who couldn't leave their own half, and we might have equalised.
"The performance tells us that if we play like we did in the first half then we risk losing to everybody, but if we play like we did after the break we can be a match for anybody."
Defender Angelo Ogbonna will return from a lengthy injury lay-off against Atalanta, against whom the Granata secured their best result of the season to date by winning 5-1 in Bergamo.
Striker Abour Diop is injured, though, while defender Danilo D'Ambrosio serves a one-match ban.
Atalanta midfielder Luigi Giorgi has faced Torino already this season during a loan spell at Palermo and he knows they can dominate any opponent on their day.
He told the Corriere dello Sport: "It will be a tough game, the Granata have a strong identity and play well-organised football.
"They're good at moving the ball forward and stopping you from getting into a rhythm. If you make any tactical errors, they punish you.
"They have quality strikers, (Alessio) Cerci is a constant point of reference for their attack and (Rolando) Bianchi is dangerous in the air.
"We have to be clever and if we can stayed focused and organised we can get a result. It's important to win these kind of head-to-heads but it's even more important to have continuity."
Midfielders Giacomo Bonaventura and Davide Biondini are suspended while Luca Cigarini, Gian Bellini, Stefano Lucchini, Michele Ferri and Guido Marilungo miss out through injury.