Team Sky sports director Gabrial Rasch reported that Thomas had a 'really bad day' on the final stage that was shortened to just 57 kilometres after adverse weather conditions ruled out the Albulapass hors categorie climb.
Thomas had previously suffered in the cold during the race's two previous mountain stages, which was put down to the weight loss he has achieved in an attempt to improve his climbing. The 30-year-old appeared to bounce back during Saturday's penultimate individual time trial stage, where he finished ninth and was placed eighth overall.
However, he could not keep pace with the front runners on Sunday and came home in 91st place, losing 11 minutes and one second to stage winner Jarlinson Pantano (IAM Cycling). He ended up 17th overall, 12-31 behind winner Miguel Angel Lopez (Astana).
"G had a really bad day," said Rasch. "He was super cold on the top of that mountain and when he knew he couldn't follow the guys and he didn't have anything to fight for he just got to the finish in his own time.
"All of the guys did well this week and tried really hard for G. That was the plan and everyone gave up their own ambitions to do that. G was just lacking that final 10 per cent to be up there."
Thomas was riding the Tour de Suisse as leader for Sky and was one of the main contenders having placed second overall last year. The Welshman has refocussed on riding stage races for 2016 rather than classics, and is hoping to put in a solid ride in the Tour de France alongside team-mate and defending champion Chris Froome.
Watch: Tour de France 2016 essential guide
Thomas went into the Tour de Suisse after a training block with Froome and other select members of Team Sky on Tenerife. Team Sky sports director Nicolas Portal told Cycling Weekly last week that both Thomas and Froome will be supported riders for the Tour.
“He’s [Thomas] never done a top five or top 10 in a Grand Tour," said Portal. "It’s step by step for ‘G’. It will be more than a dream if we have two there on the podium in the Tour."
The 2016 Tour de France starts in less than two weeks' time, on Saturday July 2. Sky has yet to confirm their nine-man roster for the race.
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