Mauricio Pochettino has admitted that a positive result against Borussia Dortmund is vital to Tottenham Hotspur's hopes of progressing in the Champions League.

The Lilywhites struggled in the group stage last time out, winning just two of their six games as they finished behind AS Monaco and Bayer Leverkusen.

Spurs have an even tougher set of fixtures this time around, with reigning European champions Real Madrid and Cypriot champions APOEL joining Dortmund in Group H.

Pochettino knows the importance of getting off to a positive start at Wembley Stadium in midweek, though he insists that it is not a case of his side battling it out for second spot behind Los Blancos.

"I think Wednesday is so important, to start well in the competition and get the three points will be key to the future," he told reporters. "In theory it should be Real Madrid first and the others trying for second, but football is not about theory. Our ambition is to win every game.

"Real Madrid are on a different level: they won the last two Champions Leagues so it's a different reality. I think it'll be a very competitive group. Last season after the first game against Monaco it was difficult to change the dynamic. It's so important to try to win the game.

"It will be tough, Dortmund are a great team, but in our mind our mentality is to win and be aggressive from the start. Last season was our first experience in the Champions League... It was a very painful experience because we couldn't be at the level we needed to be, but now that's not an excuse."

Spurs follow up Wednesday's home tie against Dortmund with trips to APOEL and Madrid over the next five weeks.