Spurs needed extra time to get past National League side Tamworth on Sunday but have progressed to the FA Cup Fourth Round while also having a 1-0 advantage in their Carabao Cup Semi-final tie over Liverpool.
However, former midfielder O'Hara thinks the squad lacks strength in depth, and there isn't enough fear from their big names over possibly losing their place in the team.
“Tottenham need to bring in players in January who can genuinely challenge for a spot in the starting eleven,” he told Grosvenor Sport.
“Look at Dominic Solanke—he’s come in and made an impact, he’s playing regularly, and he’s improving. Too many of the other signings haven’t had that same effect. If you look at the starting eleven, it’s still largely made up of players who were at the club last season.
“Tottenham need signings who will put real pressure on the starters. If someone like James Maddison or Brennan Johnson isn’t performing, they should be at risk of being dropped to the bench.
“Spurs need players who are good enough to be starting, not just filling out the squad. If they sign the right players, even someone like Heung-min Son could find himself on the bench. That’s the level of quality they should be aiming for.”
Ange Postecoglou has already been able to add to his squad with the signing of goalkeeper Antonin Kinsky, who made an impressive debut in the Carabao Cup win last week. O'Hara is already a big fan of the young Czech and believes he could provide stiff competition to current number one Guglielmo Vicario.
“Antonin Kinsky was absolutely fantastic against Liverpool in the Carabao Cup,” O’Hara added.
“To put in that kind of performance on your debut, in front of 60,000 people, under immense pressure from a Liverpool side intent on testing him, was brilliant.
“After just five minutes, his composure was clear for all to see. It’s early days, of course, but there are already clear signs that he could be a brilliant signing for Spurs.
“What stood out was how Kinsky’s presence in goal seemed to calm everyone—not just the fans but the outfield players, too. There was a real confidence in him when the ball went back to him, and that made a big difference. He absolutely deserves to keep his place in the side moving forward, especially with Vicario out injured.
“If he keeps performing like that, there’s no reason he can’t seriously challenge Vicario for the number one shirt.
"One area where Kinsky really impressed me was with his handling of crosses into the box—something Vicario has struggled with. If Kinsky continues to show that kind of performance, he could make the position his own.”