( CNN ) -- The saying goes that a bad workman blames his tools but Roger Federer refused to pin a shock defeat in Hamburg on his new racquet . Federer , who is experimenting with a larger tennis racquet at the German tennis championships , was stunned in the semi-finals by qualifier Federico Delbonis , the world no . 114 . `` He was better than me , '' said Federer , who lost a tight match 7-6 ( 9-7 ) 7-6 ( 7-4 ) to the Argentine . `` I do n't think it had much to do with the racquet . `` Both sets could have gone either way . It 's clearly a pity I could n't win either of the sets because I was starting to feel better towards the end of the match . `` Unfortunately I could n't push him further and create more chances . `` I tried everything I could at this tournament . It 's been a difficult week . '' Federer entered the Hamburg clay-court tournament to try and rediscover some form after a dismal Wimbledon . The Swiss winner of a record 17 grand slams made a shock second-round exit at the All England Club championships at the hands of 116th ranked Sergiy Stakhovsky . Part of his plan to get back to his best has been a decision to play with a larger 98-inch square frame racquet -- eight inches larger than his previous racquet . Explaining his decision to try out the racquet in Hamburg earlier this week , Federer said on the ATP Tour website : `` I 've been very close on numerous occasions to changing racquets in a bigger way . `` But then very often , time was the issue . Maybe also just the records of grand slams - I was always keeping on playing quarters and semis - so then it was also a bit more difficult to change it because of the time . `` After I lost at Wimbledon , I thought this is a good time to go and test the racquets , to take a bit of time off and then add some tournaments and see was there enough time to change or not . `` I 'm happy I did the change and now we 'll see how it goes . '' Federer -- who dropped from third to fifth in the world rankings after his Wimbledon loss -- will now head home to Switzerland to play at Gstaad next week . Delbonis now faces Fabio Fognini for the Hamburg title after the Italian beat Spain 's Nicolas Almagro 6-4 7-6 ( 7-1 ) .
Argentine Federico Delbonis loses in the semi-finals of the German Tennis Championships . Federer beaten by world No.114 Roger Federer in straight sets . The German 17-time grand slam winner is trialling a new racquet with a larger frame . Wimbledon said early Federer exit was a good time to make the switch .