Football fans around the world are watching the UEFA Champions League with keen interest but the problem is some may soon see their teams’ road to Wembley end prematurely.Surprisingly some games have ended in dramatic fashions with some of the big wings in Europe testing unpredictable defeats and unwanted draws.Spanish giants Real Madrid and Barcelona were among high profile culprits alongside English big spenders Manchester City. The most notable result of the last round of matches was registered by Scottish side Celtic this week shocked football fraternity with a memorable win over one of the title favourites Barcelona.Though the Scottish club suffered some nervy moments the end of the game, they were able to clinch a historic win on home soil. The big win in front of their own fans will go down to their history as their best European result since winning the European Cup final  in 1967 against Inter Milan from Italy.The Scottish champions have now opened door for the underdogs to stage challenge against Barcelona in the competition after they defeated the four-time European champions 2-1 with a goal scored in each half of the game.Barcelona’s last defeat in the competition was against Chelsea in the semi-finals last season. The Catalans are among the favourites to win the prized competition but the performance against Celtic exposed their weaknesses.The Spanish giants are no longer a threat like in previous years. Celtic showed good nerve strength against them in both the first and second leg matches.The Scottish side did not show too much respect against the European powerhouse led by Fifa World Player of the Year Lionel Messi as they controlled and passed the ball confidently.During the first tie in Spain, Barcelona stole maximum points with a last minute winner from Jodi Alba but the Glasgow side responded well in the second tie to inflict defeat. After this defeat, I believe underdogs will no longer fear to play against Barcelona as Celtic has already proved the Catalans are beatable. The reigning Spanish champions Real Madrid were held at home by the reigning Germany champions Borrussia Dortmund, who have been able to mix well with European’s finest since 1997 when they last won the competition.Dortmund beat Real Madrid 2-1 in Germany and looked almost destined to another memorable victory against Jose Mourinho’s side in Madrid after half time goals from talented Germany youngsters Marco Reus and Mario Gotze put them in the driver’s seat.However, the galacticos, who knocked the ball with pace and physical aggressiveness right from the start of second half, got their reward through Mesut Ozil from a well taken free-kick.  Dortmund, who leads the group, looked the better side over the two matches. Dutch champions Ajax Amsterdam put the spanner in Man City’s wheel after taking four points off Roberto Mancini’s millionaires. First a 3-1 win in Amsterdam and a 2-2 draw in England appear to be the final nail in City’s coffin as far as European competition this season is concerned.Dortmund head the group of death with 8 points, Real Madrid second with 7 points from four games played, Ajax have four, while English champions Man City have two and are likely to miss out on the group stage for the second season running.City still have an outside chance to qualify for the knock-out phase. City host Real Madrid in their next fixture before travelling to Germany to face Dortmund needing to win both and hope that Ajax don’t pick any more points in the remaining games.