That came at Wimbledon where Serena was a much more comfortable winner of Venus than she was here, and then struggled to overcome Victoria Azarenka in the Quarter Final. However, Azarenka has given Williams plenty of food for thought in matches through this season and I think this match up will be much more like one that Serena can dominate.
She won't be taking Roberta Vinci for granted though having played a tight match against her in Canada that was decided 63, 64 in favour of Williams. It had been a couple of years since Serena Williams had last played Vinci and there is no doubt that the Italian can be a very awkward customer when you haven't seen her game for a while.
The slicing and dicing Vinci employs can rattle opponents, but Williams admitted that seeing her game recently in Canada should aid her in this match. I tend to agree with her as Williams will know what to expect a lot more and should have the power to make sure she keeps Vinci pushed behind the baseline and playing on the defensive for much of the match.
The key for Williams is to clean up some of the errors that crept into her game against Venus Williams, but this opponent won't be able to hit through the court as her elder sister was able to do. Vinci will look to rattle Serena by serving well and looking to extract errors by changing up her variation and attacking the net where possible.
I am not sure that will be enough against a focused Williams who has seen what Vinci is about just last month and I think she does enough to win this by a couple clearer games in a 63, 62 victory.
Simona Halep - 4.5 games v Flavia Pennetta: Flavia Pennetta won the first three matches she played against Simona Halep including at the US Open in 2013 on her way to the Semi Final. That year Victoria Azarenka was too good for Pennetta in the Semi Final but she can use that experience to give Halep a tougher test, although it has to be noted when she beat her two years ago that the latter was still finding her consistency on the Tour.
It would be foolish to ignore the fact that Flavia Pennetta was a big underdog in that match though so she is capable of upsetting the odds. In fact the prices are very similar in that Fourth Round match compared with what we are seeing in the Semi Final so there is a chance that the Italian can dig deep again and beat out Halep to reach her first Grand Slam Final.
However, Halep was a pretty dominant winner over Pennetta when they met at the Miami Masters earlier this season and you know there will be a few breaks of serve in this one. Both players will look to dominate the rallies by pushing and prodding the other around the court and movement is going to be key.
For Pennetta her serve has to be working because Halep punished her second ball in Miami, while Halep also has to keep Pennetta at bay and is always a better player when she feels her serve is working effectively.
I've no doubt that the match will have its swings with both players likely to create a few break point chances and it will come to the fine margins of which one is most clinical when those chances arrive. Halep must have got over a hurdle mentally by beating Pennetta in Miami having lost two matches to her when she was favoured to win and I think she can earn something similar to that result and cover this number of games even though the underdogs have been flying against the handicap throughout this tournament.
Novak Djokovic - 6.5 games v Marin Cilic: Novak Djokovic is looking for his second US Open title and will be looking to reach his fifth Final in the last six years in New York City, although a four year streak of reaching the Final was ended with a surprise Semi Final loss last season.
That defeat to Kei Nishikori clearly bothered Novak Djokovic who responded with a long winning run following that defeat and he has not been quite up to the very high standards he sets for himself this year. Djokovic has dropped sets to Roberto Bautista Agut and Feliciano Lopez in the last two Rounds, although the way he handled the Spaniards in the final two sets of both of those matches was impressive.
Djokovic might have won all thirteen previous matches against Marin Cilic, but he will know he has to raise his game against the defending Champion. I have never seen Cilic so fired up as he was at the end of his Quarter Final win over Jo-Wilfried Tsonga and Djokovic was the first to point out how comfortable the Croatian has got to feel behind a twelve match winning run at this event.
It has been a surprising run from Cilic to some extent as he hadn't shown the form over the last six weeks to think this was within his range, but he has had a couple of five setters and I wonder if he physically might have a let down. Cilic has had time to recover, but mentally he has to overcome the challenge of beating a player he hasn't done before and physically he has spent a lot more time on the courts during the heat of the day.
Djokovic might not always feel comfortable in the heat, but cooler conditions usually are more to his liking. It will mean the ball doesn't fly quite as quick, while the structure of the new roof seems to have taken away some of the wind issues on Arthur Ashe which benefits the World Number 1 too.
He has won his last 9 sets against Cilic and Djokovic beat him very easily at Wimbledon despite the 64, 64, 64 scoreline. Djokovic simply got his break and managed his own game to make sure he won in three sets and I think Cilic will have a tough time in the office to turn things around.
I think Cilic will have some success as he looks to hold onto the title he won surprisingly in 2014, but I think Djokovic might have his most complete match of the tournament. It might eventually see Djokovic wear down Cilic who has to be feeling the fatigue to some extent and I think Djokovic returns to the Final after a 64, 63, 64 kind of win.
Stan Wawrinka + 4.5 games v Roger Federer: For the first time EVER for the picks, I think there is a perfectly reasonable suggestion to make TWO picks from the Stan Wawrinka versus Roger Federer Semi Final which looks like it could be a classic.
Two players that have a good relationship off the court, even if their blow up on the court at the O2 last season was out of the ordinary, will meet for a place in the final Grand Slam Final of the season. Stan Wawrinka has admitted that he used to be nervous coming out to face Roger Federer, but being a two time Grand Slam Champion has changed things a little.
While Wawrinka will be the first to admit he is nervous knowing he is up against one of the best to ever pick up a racquet, he does feel he has rattled Federer enough to actually make him a little anxious in anticipation of what will be seen on the court.
Matches between them have certainly been a lot closer in the last couple of years since Wawrinka really made a breakthrough on the Tour. Since winning the Australian Open in January 2014, Stan Wawrinka is 2-3 against Roger Federer which looks a lot better than his overall 3-16 record against his compatriot.
One of those two wins came in a very convincing straight sets win at the French Open on the way to picking up his second Grand Slam title of his career so Wawrinka might have a mental edge in that regards. Their match at Wimbledon last season was a close four setter that ended in favour of Federer and the last five matches have seen both players win a set three times.
The last two matches have seen Federer and Wawrinka win a match each in straight sets, but I would be stunned if that was the case here. There is no doubting that Federer is in incredible form and he has won 10 matches in a row since the beginning of Cincinnati without dropping a set. His SABR tactic has surprised many with the effectiveness of the shot, but Stan Wawrinka is a really dangerous customer when he gets to this stage of a Grand Slam.
Over the last three seasons, Stan Wawrinka has reached the Quarter Final or better of eight Grand Slams with this being Number 9 out of 12 Slams played. That is some great consistency, while have a quick check of the way he is beaten in those matches.
This is the third time in a row he has reached the Quarter Final or better at the US Open and the last two losses have come in five sets as Wawrinka pushed Novak Djokovic and Kei Nishikori the distance. His loss at Wimbledon in the Quarter Finals in 2014 and 2015 has seen Wawrinka go down in four competitive sets to Federer and a long five setter against Richard Gasquet. Wawrinka's defeat at the Australian Open in the Semi Final earlier this year came in five sets.
It is a trend that can't be ignored- Wawrinka is a shot-maker that has the confidence when he gets this deep into a tournament to beat the very best players on Tour or at least push them to their absolute limit if he is to be defeated.
I love what Federer has been doing on the court, but Wawrinka is unlikely to let this match slip past him easily and backing him with this number of games can be effective. However, I am also going to back this match going over the 38.5 Total Games that have been set simply because I don't believe this is going to be anything but a spectacular match where both players have to grind to their limit.
I'd be beyond stunned if this match was to finish in straight sets considering how competitive matches have been between them in recent meetings and that game tally looks a few games short to me.
MY PICKS: Serena Williams - 6.5 Games @ 1.83 Coral (2 Units)
Simona Halep - 4.5 Games @ 1.91 Bet365 (2 Units)
Novak Djokovic - 6.5 Games @ 1.91 Ladbrokes (2 Units)
Stan Wawrinka + 4.5 Games @ 2.00 Bet Victor (2 Units)
Roger Federer-Stan Wawrinka Over 38.5 Total Games @ 1.80 Ladbrokes (2 Units)
US Open Update: 35-34, - 2.35 Units (137 Units Staked, - 1.72% Yield)