Ten Hag: Man Utd not title contenders but belief is growing
Goals from Casemiro, Luke Shaw and Marcus Rashford at Old Trafford earned United a fourth league win in a row, closing the gap to leaders Arsenal to nine points.
United struggled to their worst-ever Premier League points total last season and have not won the English top-flight title since 2013, when Alex Ferguson was still in charge.
"That's a big step," Ten Hag said when asked about United's involvement in the title race.
"No, but the belief is growing and that's a good signal. We have to give every game 100 per cent energy and focus and if you keep in that philosophy it's possible (a title bid).
"We don't get too far ahead, it is January, not even half a season, the next game is Everton coming quick, so we will enjoy 24 hours and then move on."
United have won four consecutive home Premier League games without conceding a goal for the first time since a run of six between May and October 2017, and have not conceded in the league at home since a 3-1 win over Arsenal in September.
Goalkeeper David de Gea needed to make several fine saves to preserve another clean sheet on Tuesday and drew specific praise from his manager.
"We only stay strong defensively if we do our jobs and give 100 per cent in every situation," he added.
"He (De Gea) performed really well. He made some brilliant saves and today one of the reasons we have so many clean sheets is David de Gea. Against West Ham, for example, I remember a save from him. In general, we don't concede so many chances."