Djokovic has won all 13 of their previous meetings. Their last match was in July this year in Canada. He won in straight sets on a hard court.
In 6 of their 9 hard court matches Monfils has taken a set. In their last US Open meeting in 2005 it went to 5 sets although Djokovic was the lower ranked player and was just inside the top 100.
Djokovic has only had to complete 2 of his 5 matches. Vesely withdrew and both Youzhny and Tsonga retired. He has not been put under pressure which isn’t an ideal situation to take into a slam semi final.
Monfils has found some recent form that few people expected. His mind and attitude seem to be in exactly the right place.
I don’t see Djokovic taking this in 3 sets and we may even see a 5 setter. I think it is worth trying a lay on Djokovic. A 13-0 previous record has to make it tough for Monfils to truly believe he can take 3 sets