US Open 2019 betting tips: Previews and best bets for day nine at Flushing Meadows

Recommended bets

1pt Wang to win at 7/2

1pt Medvedev +1.5 games at 4/5

For details of advised bookmakers and each-way terms, visit our transparent tipping record

Serena Williams v Qiang Wang

The bottom quarter of the draw pits six-time champion Serena Williams against major-tournament-second-week debutant, Qiang Wang. Each player has a unique motivation here - Serena looking for her 24th grand slam singles title to equal Margaret Court's record while Qiang Wang is playing in memory of her former coach, doubles great Peter McNamara, who died in July.

After the commotion of last year's final, Serena was travelling along relatively quietly until the last round when she rolled her ankle against Petra Martic. That occurred early in the second set and didn't stop her at the time, but with her adrenaline pumping and Martic not doing enough to stretch Williams into all corners of the court, she got away with it. The worrisome period with an injury like that is the morning after when the body has cooled down. It might be nothing - it's not uncommon for players to tape their ankles regularly - but if there is a player left in the draw with a game to exploit any fragility in an ankle, it's Qiang Wang.

The world number 18 shocked most fans with a straight sets win over Ashleigh Barty in the fourth round, denying Barty the chance to control the court, forcing her back with great depth and angles. Wang is a momentum player - when she has a head of steam up, she gets on a roll and goes deep in tournaments, particularly on this surface. While she has not faced Serena before, over the past 12 months, she has a handy list of victims - Karolina Pliskova, Aryna Sabalenka, Elina Svitolina, Garbine Muguruza, Madison Keys, Elise Mertens, Johanna Konta, and on Sunday, Barty.

Curiously, she was scheduled to face Serena in Miami this year before the American gave a walkover due to a knee injury. On that occasion, the odds were much closer together than we have here. Perhaps the circumstances and medical reports were a little different then but it seems a little odd on the surface, considering their rankings are virtually the same.

The last time Williams was beaten before the semi-finals at Flushing Meadows was seemingly in another lifetime - 2007, before Brexit, before David Cameron was prime minister, before the global financial crisis. Yet today I think it's time. Perhaps it's a metaphor for the USA v China trade wars, perhaps it's just tennis.

I feel Serena is priced up far too short considering she is yet to play anyone of the calibre required to exploit her modest firm. Qiang Wang thrashed the world number two on Sunday and deserves more respect.

Best bet: Wang to win at 7/2

Stan Wawrinka v Daniil Medvedev

The dogs were barking just before Stan Wawrinka's clash with Novak Djokovic on Sunday night, word rapidly spreading that Djokovic's shoulder had flared up in practice, and it was on the money, with the top seed retiring in the third set and being thwarted in his quest to overcome the discomfort.

As mentioned in my preview, Wawrinka's game is awkward at the best of times for Djokovic, but with a shoulder injury, it was about the worst matchup he could find. The 2016 champion stepped up a level but the resistance simply wasn't there from the other end.

So how does he match up against Daniil Medvedev? The Russian plays with hard and flat groundstrokes rather than loopy topspin. It's a high-risk style with little margin for error, but Medvedev is on a run of 18-2 since Wimbledon, losing only to Nick Kyrgios in the Washington final, and Rafael Nadal in the trophy match in Cincinnati.

Every time he looks exhausted, he feeds off the negative energy from the crowd and finds a way to win again. He loves trolling the crowd and it fires him up. But in the press conference after the win over Dominik Koepfer, he spoke of requiring painkillers to deal with adductor and shoulder pain. Perhaps he's winding us up again but numerous people in the media have suggested he's a very nice guy off the court and unlikely to be telling porky pies.

The head-to-head stands at 1-0 to Medvedev, from a match at Wimbledon in 2017, where he defied the rankings of three versus 49.

Wawrinka has come up favourite in this match, largely because of the concern over Medvedev's fitness, which is difficult to quantify. On current form, Medvedev would be clear favourite. The risk with backing injured players is that different betting markets have different rules - the Match Result market only requires the first set to be played for payout (so bets on Djokovic against Wawrinka would have lost), while every other match market requires the match to be completed unless that market has been unconditionally determined (e.g. our No Tiebreaks bet was voided but would have been a loser had either of the completed sets been 7-6). Note, these are Sky Bet rules, other firms may have a different settlement policy on Match Result.

We can take advantage of this discrepancy by backing Medvedev on the game handicap. If he retired at 6-4 4-6 0-3, then a match win bet would be lost, while a games handicap bet would be voided. Medvedev has retired in matches several times before, so he's unlikely to be too proud to concede if the pain is proving too much for him. But I'd rather focus on the positive side - he is young, dynamic and on a roll. He is capable of winning this despite his aches and pains.

Best bet: Medvedev +1.5 games at 4/5