Mauricio Pochettino believes Dele Alli is over his dip in form after the midfielder scored Tottenham's winner against Barnsley in the Carabao Cup third round.Pochettino had admitted before the game he would start Alli at Wembley to help the 21-year-old rediscover his groove following some disappointing recent displays.And Alli duly delivered, his second-half strike proving the difference as Spurs sealed a 1-0 win and their place in round four."For me, Dele Alli is a top player. He is a key player for us. I think he helped us by scoring today," Pochettino said."I am so happy with him. It's true that everyone can do better but I am happy. It is a period that he needs to find his balance but I am so happy, his performance was good."He tried and scored and that is fantastic."A sparse crowd of only 23,926 made for a strange atmosphere at the national stadium, with the game feeling more like a youth team fixture at times than a third-round cup tie.In fact, Tottenham had played in front of only 26,244 against Gillingham at White Hart Lane this time last season, but the swathes of empty red seats certainly made the absentees more noticeable."I understand," Pochettino said."I'd like to say thank you to all the fans that were here. Maybe it wasn't possible to come. I understand that it's so difficult for the fans sometimes to come to every single game."I want to say thank you to our fans. I know they are behind us and translate their support."Tottenham dominated the contest in terms of possession but Barnsley could have taken the lead had Liam Lindsay been more precise with a free header or Ike Ugbo converted an excellent chance after half-time.But Alli finished off Kieran Trippier's pull-back in the 65th minute for his third goal of the season and to secure Spurs a hard-fought victory."I want to congratulate our opponents Barnsley because they defended very well," Pochettino said."I think it was a very tough game, how they defended and played it was difficult for us to create chances. Today, yes, I think our opponent was so tough because we could not shoot on target in the first 60 minutes."