Marta Kostyuk vs Liudmila Samsonova Prediction — Guadalajara, Thursday, September 17, 2026

Our Marta Kostyuk vs Liudmila Samsonova prediction for Thursday, September 17, 2026 (12:00 PM ET) in Guadalajara starts with a clean read: Kostyuk grades out as the stronger player on the numbers, and the market agrees, pricing her at -333. The model's own reasoning lands on Kostyuk too.

That still isn't a bet. This one is a PASS on the card: an official read with no wager attached. We're not backing either side here, and we're not going to pretend the case for Kostyuk is a case for staking her.

Why the model still likes Kostyuk

Strip out an error in Kostyuk's Guadalajara line (her round of 16 result was a walkover after Taylor Townsend fell ill, not a played win) and her corrected record still reads well ahead of Samsonova's across every window: 35-9 year to date against 18-21, 37-11 over twelve months against 21-24, and 13-4 over the last three months against 11-6, the exact stretch where Samsonova's serve numbers have improved most.

The service splits back it up. On hard courts, Kostyuk holds at 74% and breaks at 39%; Samsonova holds at 70% and breaks at 33%. Both numbers favor Kostyuk. Her clearest same-surface form line is the August 19 win over Mirra Andreeva in Cincinnati, 4-6 6-0 6-2, a result the model grades as earned rather than gifted: 31 of 43 first serves won, five breaks in six chances, and 25 winners over the final two sets.

Rested, not tested

Here's the catch, and it's the whole reason this stays a PASS. Kostyuk has played zero sets and zero minutes in Guadalajara. Her only path to the semifinal so far is a first-round bye plus that Townsend walkover, so there is no current-event form to lean on.

Her last real match was a three-set loss to Linda Noskova on September 6 (147 minutes), part of a 295-minute stretch across three matches from September 3 to 6. Since then: ten full days without a played match. Some of that gap is a wrist issue. Kostyuk reported pain that began in Cincinnati and worsened through the US Open, rested it in a splint starting September 9, and a September 15 tournament report calls her fully fit heading into Guadalajara. But there's no completed match after treatment to confirm it. She's rested. She hasn't been tested.

Samsonova's second serve is where that matters most. Kostyuk's game plan is to protect her own first serve and lean on Samsonova's second, and if the wrist limits her response on return, that's the plan's weak link.

Samsonova's counterpunch

Samsonova has actually played in Guadalajara, twice, and both wins were competitive: a 7-6(4) 2-6 7-6(5) escape against Kayla Day and a 7-6(6) 6-2 win over Elsa Jacquemot, both against lower-ranked opponents. Across those two matches her weighted service numbers are mixed: 57.0% first serves in, 63.7% won on the first, 51.9% won on the second, and 12 double faults over 179 service points. That's match practice, not proof she's rounded into form.

Her broader three-month serve improvement is real, but it's also uneven; her one-month first-serve-points-won rate sits at 63.1%, well below Kostyuk's 70-74% range over comparable stretches. If Samsonova restores her better three-month level and attacks early, particularly off that untested Kostyuk wrist, she has a route to the upset. The model also notes Samsonova is 2-6 against players who lean on first-strike tennis the way Kostyuk's plan requires, holding just 63% and breaking only 27% in those matches, with losses to Gauff and Joint showing how it goes wrong for her when the point gets extended. The two have met before, on hard courts in Beijing, but not since October 2023, so that history carries limited weight here.

The verdict

Kostyuk is the side the model likes at -333, built on a deeper resume, better hold and break numbers, and a proven same-surface ceiling win over Andreeva. But an idle, wrist-affected favorite with zero sets played in this event isn't a profile we're staking against a player who has already survived two tight matches to get here. PASS. No official action on this one.