The Daily Lob

Where the tournament stands

Friday's quarterfinals went almost entirely against the favourites. Brandon Nakashima lost a thirteen-minute first-set tiebreak 11-9 to a Taylor Fritz serving 22 aces, then won 7-6(9) 4-6 6-3 in 2h13 — a second straight Masters semifinal, and the first player outside the top twenty to reach both the Montreal and Cincinnati last four since 1990. Frances Tiafoe needed four match points, having been broken serving for it, to beat Lorenzo Musetti 7-6(2) 7-5; the two Americans meet today in Cincinnati's first all-American men's semifinal since 2010. Sara Bejlek continued the run of the tournament, beating Madison Keys 3-6 6-4 7-6(5) from 4-2 down in the deciding tiebreak — a third Grand Slam champion in a week, after Krejčíková and Sabalenka. Only Coco Gauff obliged the market, taking 71 minutes over Marta Kostyuk, who served eight double faults to Gauff's one. All four semifinals are today on P&G Stadium Court; the finals are tomorrow from 2 PM ET.

Yesterday's brief, scored

Four items, all played. The favourite won one — the worst day for the market since the brief began, on a card of quarterfinals.

	Match	Market	Result
01	Musetti v Tiafoe	53 / 47	Tiafoe 7-6(2) 7-5 — on a fourth match point underdog
02	Gauff v Kostyuk	55 / 45	Gauff 6-2 6-2, in 71 minutes favourite
03	Fritz v Nakashima	63 / 37	Nakashima 7-6(9) 4-6 6-3 — 2h13 underdog
04	Bejlek v Keys	34 / 66	Bejlek 3-6 6-4 7-6(5) — from 4-2 down in the breaker underdog

Every workload flag pointed the right way, and the tired man won anyway. Nakashima was flagged here on thirteen matches and thirty-two sets in thirty days, the heaviest load the brief has recorded, against a Fritz who had not played a third set since 3 August. He lost a thirteen-minute first-set tiebreak 11-9 to a man serving 22 aces, and won in three. Bejlek was flagged for a post-midnight finish and the shortest turnaround in the draw, and beat Keys from a set down. Fresh legs remain an edge, not a rule — and this was the day the rule broke hardest.

Tiafoe, two weeks after hand surgery, needed four match points to close out Musetti, having been broken serving for it. That flag was carried as a risk; it read as a reason he might lose rather than a reason he would win.

Four days, one pattern. The selected matches have now gone to the favourite 12 times in 26 — still under half, on cards chosen for being hard to call. The excluded matches stand at 10 in 12.

Elo's first day, scored

The rating debuted yesterday. Set against the market on the same four matches, it was closer to the truth on 3 of them — including the one where it disagreed about who was favourite.

Match	Market	Elo	Won
Musetti v Tiafoe	52.6	43.7	Tiafoe	Elo closer
Gauff v Kostyuk	54.8	60.3	Gauff	Elo closer
Fritz v Nakashima	62.5	53.4	Nakashima	Elo closer
Bejlek v Keys	34.0	30.6	Bejlek	market closer

Percentages are for the first-named player; "closer" means the smaller error against the actual result. The headline is item 01: the market made Musetti a 52.6% favourite, Elo made him a 43.7% underdog, and Tiafoe won. On item 03 both had Fritz ahead, but Elo had him at 53% where the market had 63%, so it lost by less. Only Bejlek v Keys went the market's way, and only because Elo was even more confident in Keys than the books were.

Four matches is not evidence. A twelve-day-old rating file beating a live betting market three times in one day is the sort of result that reverses itself in a week, and the honest expectation is that the market wins over any decent sample — it prices injury, fatigue and last night's tennis, and Elo prices none of them. The reason to keep both on the page is not that one is better. It is that when they disagree, the disagreement usually has a name. Today it has two: Pegula v Świątek, fifteen points apart because the file predates a Toronto title, and Bejlek v Gauff, eight points apart because it predates her entire week.