The Seattle Mariners host the Cincinnati Reds on July 21, 2026. First pitch from T-Mobile Park is scheduled for 9:40 p.m. EDT. The game will be broadcast on SEAM.
The Mariners are favored by -112 on the moneyline. The Reds are -104 on the moneyline and -1.5 on the run line. The total is set at 7.5 runs.
Find my MLB picks and Reds vs Mariners prediction below, as well as probable pitchers, weather report, and more.
Reds vs Mariners Prediction
- Reds vs Mariners Pick: Mariners Moneyline (-112)
My Reds vs Mariners best bet is Seattle Mariners Moneyline. Make sure to find the best odds by checking our live MLB odds page.
Reds vs Mariners Odds
| Reds Odds | ||
|---|---|---|
| Spread | Total | Moneyline |
-1.5 +158 | 7.5 -110o / -110u | -104 |
| Mariners Odds | ||
|---|---|---|
| Spread | Total | Moneyline |
+1.5 -192 | 7.5 -110o / -110u | -112 |
- Reds vs Mariners moneyline: Reds -104, Mariners -112
- Reds vs Mariners over/under: 7.5 (-110 / -110)
- Reds vs Mariners spread: Reds -1.5 (+158), Mariners +1.5 (-192)
Reds vs Mariners Probable Pitchers
| RHP Chase Burns (CIN) | Stat | RHP Luis Castillo (SEA) |
|---|---|---|
| 11-1 | W-L | 3-8 |
| 2.9 | fWAR (FanGraphs) | 0.9 |
| 2.54 / 3.17 | ERA / xERA | 4.93 / 4.56 |
| 3.41 / 3.60 | FIP / xFIP | 4.16 / 4.43 |
| 19.6% | K-BB% | 13.6% |
| 36.1% | GB% | 37.4% |
| .264 | BABIP | .303 |
| 113 | Stuff+ | 98 |
| 100 | Location+ | 110 |
Reds vs Mariners MLB Betting Preview
Cincinnati Reds Betting Preview
The Reds are positioned as one of the most notable sellers of the upcoming trade deadline. They are dead-last in the NL Central, with a 45-54 record and six games separating them from fourth place.
While there is young star talent on the roster, there is not enough to make a run in a strong division. Spencer Steer, Tyler Stephenson, Eugenio Suarez, Emilio Pagan, and Brady Singer should all be playing elsewhere by August.
The Reds need to focus on maximizing their upcoming window of primes between Elly de la Cruz, Sal Stewart, Hunter Greene, and today's starter, Chase Burns.
They just rewarded Burns with an extension and would be wise to maximize their potential while he and the rest of this core are healthy.
For the time being, Cincinnati would be wise to give young players like Rhett Lowder, Edwin Arroyo, Noelvi Marte, and Chase Petty consistent opportunities to see what they could potentially provide in the future.
Seattle Mariners Betting Preview
The Mariners continue hovering around .500 despite having the roster construction of an AL contender. Their rotation is one of the best in baseball, their offense is above average, and their bullpen is very good.
Unfortunately, they are inconsistent and have not received any notable production from the 2025 AL MVP runner-up, Cal Raleigh.
Raleigh provided a grand slam in their 8-0 win over the Reds last night, but one home run is not a turnaround. His 10 HR and 31.8% K this season are a far cry from his 60 HR and 26.7% K in 2025.
The Mariners' hottest hitters lately are 22-year-old Cole Young and Dominic Canzone. Their production is keeping the offense alive while Raleigh and the veteran Josh Naylor struggle.
The offense could be very good if everyone is healthy and in sync, but that has not been the case for an extended period. If Seattle adds a power hitter at the deadline, their season should find an immediate spark.
Reds vs Mariners Pick, Betting Analysis
The Mariners seldom have a pitching disadvantage, yet there is a gap between them and the Reds today. Chase Burns is one of the best starters in baseball. He has leaped from a budding, young SP in 2025 to an ace in 2026.
Meanwhile, the Mariners are starting former frontline starter Luis Castillo today. Castillo's season is a classic "tale of two halves".
First 9 outings: 6.34 ERA, 6.08 xERA, 4.50 xFIP, 1.37 WHIP, 34.1% GB rate
Last 9 outings: 3.50 ERA, 3.23 xERA, 4.33 xFIP, 1.17 WHIP, 40.9% GB rate
Castillo is not striking out more batters or walking fewer, but he is generating weaker contact and more ground balls.
Today's bet is leaning on this recent trend, along with Chase Burns' stretch since June 27. He has allowed 10 runs in 17 innings during this span, with a season-high six walks in his last start.
Also, Seattle's offense is much better against RHP this season (105 wRC+) than the Reds (86 wRC+). The Reds' lineup cannot start more than five left-handed hitters, making them vulnerable against RHP.
With at least four right-handed bats in the Reds' lineup, Castillo can leverage his excellent splits against RHH (19.3% K-BB, 3.23 xFIP) and his favorable home splits to eat innings today.
Even with Julio Rodriguez potentially injured, the Mariners have the far better offense and bullpen, giving them a good shot to win if Castillo's start is respectable.
Pick: Mariners Moneyline (-112)
