Quinn Mathews MLB Debut: How to Watch Cardinals-Blue Jays

Quinn Mathews threw 156 pitches in a college baseball game once.

It was June 2023, a Super Regional against Texas, and Stanford’s left-handed ace went the distance in a complete game that people are still arguing about three years later. Some called it heroic. Others wrote pieces predicting his elbow would not survive it.

His elbow survived it. On Saturday afternoon in Toronto, at 3:07 p.m. ET, he makes his Major League debut.

One note before anything else: it is spelled Mathews, with one T. Autocorrect will fight you. Or add an apostrophe.

How to watch Quinn Mathews’ MLB debut

• Matchup: St. Louis Cardinals (54-56) at Toronto Blue Jays (51-59)
• First pitch: 3:07 p.m. ET / 2:07 p.m. CT, Saturday, Aug. 1
• Venue: Rogers Centre, Toronto
• Cardinals TV: Cardinals.TV
• Blue Jays TV: Sportsnet, TVA Sports
• Stream: Fubo, or MLB.TV out of market
• Cardinals radio: KMOX 1120 AM / 104.1 FM
• Blue Jays radio: SN590 The Fan
• Probables: Quinn Mathews, LHP, No. 60 (MLB debut) vs. Kevin Gausman, RHP (4-10, 4.51, 123 K)

Cardinals lineup: JJ Wetherholt 2B, Jordan Walker RF, Alec Burleson 1B, Iván Herrera DH, Lars Nootbaar LF, Masyn Winn SS, Nathan Church CF, Blaze Jordan 3B, Jimmy Crooks C.

Blue Jays lineup: Luis Urías 2B, Vladimir Guerrero Jr. 1B, Kazuma Okamoto 3B, George Springer DH, Alejandro Kirk C, Daulton Varsho CF, Ernie Clement SS, Myles Straw RF, Davis Schneider LF.

The roster moves

St. Louis selected Mathews’ contract from Triple-A Memphis on Saturday morning. To clear a 40-man roster spot, the Cardinals designated right-hander Tink Hence for assignment. Matt Svanson was optioned to Memphis for the active roster spot.

Hence is a real cost. A second-round pick in 2020, he was drawing top-100 prospect attention as recently as last year, and Baseball America and MLB Pipeline both still rank him 28th in the system. But a lat strain, chest tightness and shoulder problems piled up, and St. Louis moved him to relief at Memphis to manage the workload. He has a 6.64 ERA and an 18.2 percent walk rate over 20.1 innings in his first Triple-A season.

He turns 24 this week. With Monday’s 6 p.m. ET deadline two days away, a trade is more likely than waivers.

Cardinals Bullpen Blows Leahy’s Gem in 3-1 Loss to Blue Jays

Stanford Cardinal to St. Louis Cardinals

Stanford’s nickname is the Cardinal — singular, and it refers to the color, not the bird. Mathews spent four years there and left as one of the most decorated arms in program history.

He pitched in three College World Series. He was a Golden Spikes Award semifinalist in 2023. And on June 11, 2023, against Texas in a Super Regional, he threw the complete game that made his name — 156 pitches, in an era when major league starters are pulled at 100.

The Cardinals took him in the fourth round, 122nd overall, six weeks later.

Rise, stall, rise

His first professional season was a monster. In 2024 he posted a 2.76 ERA across 143.1 innings with 202 strikeouts, was named Baseball America’s Minor League Pitcher of the Year, and became only the second minor league pitcher to clear 200 strikeouts since 2011. MLB Pipeline ranked him the 45th-best prospect in baseball entering 2025.

Then it stopped. Left shoulder trouble, lost fastball velocity, mechanics that would not settle. He finished 2025 with a 3.93 ERA over 94 innings and fell off the national lists.

The command problems carried into this spring. Then they stabilized, and everything else came back with them.

Over 19 starts at Memphis this season he is 3.13 with 111 strikeouts in 92 innings. Over his final 10 starts, 1.59. He worked at least six innings in each of his last four outings, and in his last one on July 24 he went seven scoreless with 10 strikeouts on three hits and three walks.

Why this matters more than one start

The Cardinals do not miss bats. Their rotation has been built on ground balls and soft contact — Andre Pallante, Michael McGreevy, Kyle Leahy — and it has worked well enough without ever producing the kind of arm that ends an inning by itself.

Mathews is that arm. His slider and changeup generate the whiff rates the organization has been hunting for, and the fastball plays behind them. A controllable left-handed starter with swing-and-miss stuff is exactly what a front office rebuilding a pitching pipeline wants to see before it makes deadline decisions.

The timing is not accidental. Monday is the deadline. Dustin May is in every rumor. Giving Mathews the ball now lets St. Louis see what it has before it decides what to trade — and the last Cardinals pitching prospect to debut with this kind of pedigree was Matthew Liberatore in 2022.

What the market says

The most telling number is not a strikeout line. It is the fact that FanDuel is pricing this game in five-inning increments.

St. Louis is +114 to lead after five, +148 to win the first five outright, with a tie at +470. Toronto is -142 and +100 respectively. The first-five total sits at 4.5, over -120 and under -108. That is a market that expects Mathews to be gone before the seventh, which is how the Cardinals have used nearly every starter not named Dustin May this season.

Mathews strikeouts, over/under 4.5: Over +136, Under -174. The under implies roughly 63 percent.

Alternate strikeout lines:

• 3+ strikeouts: -520
• 4+ strikeouts: -200
• 5+ strikeouts: +136
• 6+ strikeouts: +280
• 7+ strikeouts: +600

Combined with Gausman, 10-plus strikeouts sits at -114, climbing to +1260 for 15 or more.

You can also bet the first man he faces. Luis Urías, leading off for Toronto, is -112 for any other out or outcome, +370 to strike out, +630 to walk or be hit, +520 to single and +920 for an extra-base hit in his first plate appearance.

Odds via FanDuel as of 12:52 p.m. ET Saturday and subject to movement. Implied probabilities include the sportsbook’s margin.

Baseball without borders

Mathews debuts on foreign soil against a lineup that spans four countries.

Vladimir Guerrero Jr., batting second, was born in Montreal while his father played for the Expos. Kazuma Okamoto, hitting third with 24 home runs, came to Toronto from Japan’s Yomiuri Giants. Alejandro Kirk and Luis Urías were both born in Mexico — Kirk in Tijuana. Behind them, Toronto’s roster runs through the Dominican Republic and Venezuela.

St. Louis answers with Iván Herrera of Panama City hitting fourth, a 2026 World Baseball Classic participant for Panama.

Gausman is 4-10 with a 4.51 ERA, the most forgiving assignment a debuting starter could draw on the road.

The Cardinals lost 3-1 on Friday night when the bullpen gave away six innings of one-run work from Leahy. They are 54-56, fourth in the National League Central, and Saturday is the first look at what comes next.