Postpublished at 21:16 British Summer Time 9 September 2016
Djokovic 6-3 3-1 Monfils
David Law
Radio 5 live sports extra commentator
Nobody is really applauding because they are dispirited about what they are seeing.
Djokovic & Wawrinka through to US Open final
Stan Wawrinka (Swi) beats Kei Nishikori (Jpn) 4-6 7-5 6-4 6-2
Novak Djokovic (Ser) beats Gael Monfils (Fra) 6-3 6-2 3-6 6-2
5 Live sports extra commentary
Matthew Henry and Michael Emons
Djokovic 6-3 3-1 Monfils
David Law
Radio 5 live sports extra commentator
Nobody is really applauding because they are dispirited about what they are seeing.
Djokovic 6-3 3-1 *Monfils
Novak Djokovic has decided the best way to stay on top is to impose himself and attack. He repeatedly comes into the net and it is successful, with Monfils making another unforced error - that is 18 already for him.
Djokovic has won 12 of 13 points and the second set is getting away from Monfils.
*Djokovic 6-3 2-1 Monfils
Jeff Tarango
Former professional tennis player on 5 live sports extra
At first Monfils was provoking Novak but it is now provoking for me because I don't want my kids to see this.
*Djokovic 6-3 2-1 Monfils
OK, this is all a bit weird. Monfils loses his service game to love. Is he carrying a knock or trying to conserve energy for an assault later on?
The world number one is back in charge of the set. He has a break of serve and this is going to take some recovery from this position for Monfils.
Djokovic 6-3 1-1 Monfils*
David Law
Radio 5 live sports extra commentator
I can only think there is something wrong with Monfils.
Why would he totally abandon what has served him so well in this tournament?
This is not normal.
Djokovic 6-3 1-1 *Monfils
That game was a bit more of what we had seen earlier, with Djokovic winning his service game to love, including a delightful lob over the 6ft 4 in Monfils who had sauntered forward to the net. 1-1 in set two.
*Djokovic 6-3 0-1 Monfils
David Law
Radio 5 live sports extra commentator
I don't understand what is going on in this men's semi-final.
It is not like anything I have ever seen before.
*Djokovic 6-3 0-1 Monfils
Maybe Gael Monfils' tactics were to play with Novak Djokovic's mind and come out strong in set two.
Well, in the opening game of the second set Monfils quickly has to battle to save a break point, which he does by changing things up to serve-volley.
The crowd then get some great entertainment as Djokovic stands, imposing and dominant at the net blocking everything Monfils tries to get past him.
A lob from Monfils sends Djokovic scuttling back and he gets a racquet to it, with Monfils getting a lucky break as his next effort clips the top of the net and dribbles over for the game.
Djokovic 6-3 0-0 *Monfils
Jeff Tarango
Former professional tennis player on 5 live sports extra
I had my finger on a red button for if Novak had double faulted there.
I was going to press the red button to get a doctor out there for in between his ears.
Djokovic 6-3 0-0 Monfils*
David Law
Radio 5 live sports extra commentator
I had absolutely no idea what to make of that. How do you define not trying?
Djokovic 6-3 *Monfils
Monfils, one of the fastest players in the game, is playing the match at what looks to be a walking pace - playing deep off the baseline and hitting with as little pace as possible.
It is a tactic no-one was expecting, but earns him two break points.
However, at 30-40 down, Djokovic punches a serve tight into Monfils' chest to save himself.
After missing four earlier set points, Djokovic takes the fifth one as Monfils' return goes too long. A bizarre, bizarre set of tennis, and one Djokovic takes 6-3.
*Djokovic 5-3 Monfils
Russell Fuller
BBC tennis correspondent on BBC Radio 5 live sports extra
Monfils is playing with Djokovic's mind and it is paying dividends.
His game has fallen apart as Monfils has employed some rope-a-dope tactics.
*Djokovic 5-3 Monfils
OK, who thought this set was a formality? OK, I was one of them, but Monfils, who at times has given the impression of a man waiting to lose the set and get on with the match, has now won three games in a row.
Now Monfils faces the tough part. He has to break Djokovic's serve once again.
Djokovic 5-2 Monfils*
Jeff Tarango
Former professional tennis player on 5 live sports extra
That was almost like a boxer who has put his arms down by his waist and the opponent was refusing to punch him.
Djokovic 5-2 Monfils*
Djokovic 5-2 *Monfils
We were hoping that Monfils would have got some confidence after winning his first game of the match. Djokovic quickly moved to three set points, but Monfils saves all three to hang in there.
From 40-love, to advantage Monfils, but his first chance of a break back is wasted by sending a forehand long.
But wait just a minute. Wait just a minute.
The Frenchman gets another chance and a double fault from Djokovic, who for some reason is rattled at the fact the big screens in the arena are turned on, sees Monfils win the game to keep the set alive.
*Djokovic 5-1 Monfils
Russell Fuller
BBC tennis correspondent on BBC Radio 5 live sports extra
Well played Monsieur.
*Djokovic 5-1 Monfils
At 30-30, a miss-hit forehand from Monfils goes wide on the left-hand side. Monfils challenges but the video replay goes against him to take Djokovic to a set point.
A 126-mph ace saves Monfils and we go to deuce in the sixth game.
The crowd want to see a match develop and Monfils finally gets on the board with a delightful slice past a stretching Djokovic and then another monster serve for an ace.
A much-needed game for Monfils.
Djokovic 5-0 Monfils*
Russell Fuller
BBC tennis correspondent on BBC Radio 5 live sports extra
Monfils has had a shocking start. Whether it is the occasion, the nerves or he is just having one of those days, we shall see.
Could this be a sub-20 minutes first set?