1st set, Federer was playing his usual dominating style. won 6-0.
2nd set, Federer noticed that Coria was contemplating whether to throw in the towel and retired due to his heavily taped ankles and feet and looking lack-lustre. Federer might have gotten affected because he wanted more match practise before his semifinals. So he started playing badly, letting Coria have some motivation. Federer started playing better at 0-5 down, but Coria started to really believe there is something mentally disturbing Federer and he actually have a chance...Coria's confidence was growing and developing into a small "orange" tiger. Federer did not have much match practise, that's why the matches before Coria, he also lost the 2nd set with Nalbandian and Ljubicic after dominating the 1st set. Federer might have difficulties sustaining his level of concentration in the 2nd sets for all these matches because of his lack of match play. Another point why the 2nd set went this way was the fact that Federer played a very mentally absorbing match with Ljubicic and he was mentally drained. Likewise, Ljubicic also suffered a very disappointing loss to Federer and was mentally drained, that's why Ljubicic was very lacklustre and was mentally out of sorts when he played Nalbandian. Nalbandian also had a disappointing loss to Federer but Nalbandian got a good win against Coria, so Nalbandian's mood into his match against Ljubicic was positive and a winning outlook. But Ljubicic scored a win against Coria in his 1st match, lost his 2nd match narrowly against Federer, so Ljubicic was in a negative and had a defeated outlook. If Ljubicic had played Federer in his 1st match, Coria in his 2nd match, then played Nalbandian in the 3rd match, Ljubicic should win his match against Nalbandian but with a closer score. So I believe Federer might have also be feeling a bit of a mental drain or he might feel abit of an awkwardness because Nalbandian and Ljubicic had given him tough 3 setter matches and here is Coria giving him a 6-0 set and almost wanted to retire. Federer got affected or in his heart and mind, he was confident of letting a set go, so he just simply swung freely and tried out some net plays, looping shots, down-the-line shots which had no effort and just sailed wide and long.
Another point might be going on in Federer's mind that Federer feels that he is an Ambassador for tennis as a No. 1 and an Ambassador for this Master Cup and Federer opened the new Shanghai stadium. And with all these pull-outs by the top players, he felt bad that if he played too good and Coria retired from the match, the Chinese fans will be further disappointed.
I was expecting Federer to come back after 0-5 and win 7-5 but I think he got too used to giving up points with all his errors that it is very hard to gain back his supreme form like in the 1st set. But his final game in the 2nd set was an improvement of form compared to the rest of the 2nd set. Another possibility is that players like Sampras and Federer always play a poor match before a major match. Federer does not want to peak too fast, he wants to pace himself for the semifinals and peak ultimately for the finals. Federer also does not want to humiliate Coria 6-0 6-0 and Coria have some revenge grudge against him when they meet at a big match venue like French Open when Coria is comfortable with the clay surface and Federer has also the motivation factor to improve on his next performance with Coria after a poor 3 sets win at Masters Cup. Federer was not at all worried because this match was quite redundant because he already secured the semifinal berth but he still wants to win it because of all his winning streaks are at stake. Even his GF Mirka was Smsing on her handphone, not really bothered with the match.
Coria and his team and wife were perplexed at winning the 2nd set and were enjoying the match itself.
3rd set, Federer's opening game...He was playing like the 1st set, hitting good backhands and forehands, blasting balls into court, which is a telling sign that he unconsciously or deliberately played badly in the 2nd set. Because the transformation of his improved play was like a switch, an immediate drastic turnaround, from bad to world-class, which is astounding. Coria was also happy that he got a set from Federer, that's why Coria was grinning so much when he shook hands with Federer after the match. Coria knew he had no chance in the 3rd set and went back to serving woes and kept serving double faults.
This is what I feel about what happened in the match.
