Two unbeaten fighters, zero losses between them, and a fast track to a full world title on the line: on September 27 at Toyota Arena in Tokyo, former WBA minimumweight champion Ryusei Matsumoto (8-0, 4 KOs) meets Russell Acosta (17-0, 6 KOs) for the interim WBO minimumweight title — and the winner is in line for an even bigger prize. Reigning unified WBO/WBA 105-pound champion Oscar Collazo had been due to move up to flyweight against Ricardo Sandoval on October 10, at which point the WBO said the Matsumoto-Acosta winner would be elevated to full champion — but Collazo withdrew from that fight with a rib injury on September 19, so the exact elevation date is now unconfirmed even though the succession plan itself stands.
| Date | Sunday, September 27, 2026 |
| Venue | Toyota Arena, Tokyo, Japan |
| Event | Prime Video Boxing 16 — Inoue vs. Tenshin II |
| Division | Minimumweight (105 lbs), 12 rounds |
| Title | WBO Interim World Minimumweight Championship |
| Broadcast | DAZN (US & UK); Prime Video (Japan) |
The bout is part of a four-title undercard supporting the Takuma Inoue vs Tenshin Nasukawa WBC bantamweight rematch, alongside Tomoya Tsuboi vs Ricardo Malajika for the vacant WBC super flyweight title and Ryosuke Nishida vs Sam Goodman for the interim IBF super bantamweight title. Boxing Data tracks every title fight on the card through the fighters endpoint, including full records, physical measurements and recent form for both men in this bout.
Ryusei Matsumoto, 28, of Japan, arrives as the reigning WBA minimumweight champion, having won the belt in September 2025 and defended it once since. His route to the title was unusual: he beat Yuni Takada by unanimous technical decision after an accidental clash of heads forced a stoppage in round five, then settled the argument in the rematch six months later with a shutout 120-108 decision on all three cards over the full twelve rounds. That second fight is the one that matters here — it showed Matsumoto can carry a title-fight pace deep into a fight without fading, not just win on a technicality. He’s a southpaw standing 5’3” with a 61-inch reach, and four of his eight wins have come by knockout, including a fourth-round stoppage of John Kevin Jimenez in July 2025.
Russell Acosta, 27, of Merida, Yucatan, Mexico, is the more experienced professional in the ring by a wide margin — 17 fights to Matsumoto’s 8, and a career that started in 2020, three years before Matsumoto turned pro. He’s an orthodox fighter who has fought almost exclusively in his home state of Yucatan against Mexican domestic-level opposition, most recently a unanimous decision over Mario Cardenas in June 2026 and a tenth-round stoppage of Colombia’s Edinson Martinez in a fight both camps admitted was closer than the record suggests. Acosta hasn’t lost, but he also hasn’t fought outside Mexico, and this is by far the biggest stage and toughest name of his career. His reach checks in around 62.5 inches to Matsumoto’s 61, giving him a slight edge on paper in physical dimensions, but reach alone hasn’t been the deciding factor in Matsumoto’s two most recent championship fights.
Boxing Data’s divisions endpoint tracks every fighter active at minimumweight (105 lbs), the lightest weight class in professional boxing — the numbers below come straight from that dataset.
| Ryusei Matsumoto | Russell Acosta | |
|---|---|---|
| Age | 28 | 27 |
| Height | 5’3” | 5’2” |
| Reach | 61” | 62.5” |
| Record | 8-0-0 (4 KOs) | 17-0-0 (6 KOs) |
| Stance | Southpaw | Orthodox |
| Pro rounds | 49 | 98 |
Matsumoto — last three completed fights
| Result | Opponent | Method | Round |
|---|---|---|---|
| Win | Yuni Takada | UD | 12 |
| Win | Yuni Takada | TD | 5 |
| Win | John Kevin Jimenez | TKO | 4 |
Acosta — last three completed fights
| Result | Opponent | Method | Round |
|---|---|---|---|
| Win | Mario Cardenas | UD | 10 |
| Win | Edinson Martinez | TKO | 10 |
| Win | Roberto Ruiz | UD | 10 |
The gap here isn’t power or record — it’s the level of opposition each man has actually been tested against. Matsumoto has fought a full twelve rounds at world-title pace against a live domestic rival and come through it comfortably; Acosta has built his 17-0 record almost entirely against Mexican regional-level competition in his home state, without a signature win outside Yucatan or a fight scheduled past ten rounds. Acosta’s slight reach advantage could help him control range early, but Matsumoto’s southpaw stance has already proven awkward enough to produce four knockouts in eight fights, and his last three opponents have all gone the distance or been stopped by him — never the other way around.
The scheduled twelve rounds should favor whichever fighter can dictate the pace early. If Acosta can use his experience and reach to keep this at a comfortable range, he has a puncher’s chance to make it competitive. If Matsumoto imposes his southpaw jab and turns this into the kind of grinding fight he’s already won twice this year, the champion’s tested championship pedigree becomes the deciding factor.
Ryusei Matsumoto wins if:
Russell Acosta wins if:
ProBoxingOdds lists Matsumoto as a heavy favorite at -550 (roughly 2/11 fractional) to Acosta’s +360 (roughly 18/5) at review time. That price reflects the gap in what each man has actually proven: a champion who has gone twelve championship rounds and won every card, against a challenger with a spotless record built almost entirely at home. Acosta’s inexperience against elite-level opposition is the single biggest swing factor in this fight.
Prediction: Ryusei Matsumoto, unanimous decision.
| Country | Broadcaster | Local Start Time |
|---|---|---|
| United States | DAZN | 4:00 AM EDT |
| United Kingdom | DAZN | 9:00 AM BST |
| Japan | Prime Video | 5:00 PM JST |
Times reflect Amazon Japan’s official Prime Video Boxing 16 listing, which sets a 5:00 PM JST card start; DAZN carries the same card live in the US and UK.
The stakes here go beyond the interim WBO strap. The Ring confirmed that the WBO planned to elevate the Matsumoto-Acosta winner to full champion once Oscar Collazo vacated the belt by moving up to challenge Ricardo Sandoval at flyweight — but Collazo’s rib injury has pushed that fight back past its original October 10 date, so the winner in Tokyo becomes the WBO’s leading claimant to a vacant title with no confirmed date for the promotion to become official. It’s a genuinely consequential title fight buried on a card that also features the Inoue-Nasukawa rematch, Tomoya Tsuboi’s world-title bid against Ricardo Malajika, and Ryosuke Nishida vs Sam Goodman for the interim IBF super bantamweight title on the same night in Tokyo.
When is Ryusei Matsumoto vs Russell Acosta? Sunday, September 27, 2026, at Toyota Arena in Tokyo, Japan.
What title is on the line? The WBO Interim World Minimumweight Championship. Matsumoto is also the reigning WBA minimumweight champion.
What are Matsumoto’s and Acosta’s records? Matsumoto is 8-0 with 4 knockouts; Acosta is 17-0 with 6 knockouts.
How can I watch Matsumoto vs Acosta? DAZN carries the card in the US and UK; Prime Video streams it exclusively in Japan, with a 5:00 PM JST start per Amazon Japan’s official listing (4:00 AM EDT / 9:00 AM BST).
Who is favored to win? Bookmakers list Matsumoto as a heavy favorite at roughly -550, with Acosta around +360.
What happens to the winner after this fight? The WBO planned to elevate the winner to full champion once Oscar Collazo vacated the title by moving up to face Ricardo Sandoval at flyweight. Collazo has since withdrawn from that fight with a rib injury, so the succession plan stands but the elevation date is no longer confirmed.
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