The Kansas City Royals host the Seattle Mariners on May 23, 2026. First pitch from Kauffman Stadium is scheduled for 4:10 p.m. ET. The game will be broadcast on Fox Sports 1.
The Mariners are favored by -142 on the moneyline and by -1.5 on the run line. The Royals are +120 on the moneyline and +1.5 on the run line. The total is set at 8.5 runs.
Find my MLB picks and Mariners vs Royals prediction below, as well as probable pitchers, weather report, and more.
Mariners vs Royals Prediction
- Mariners vs Royals Pick: Under 8.5 (-105, play to -8)
My Mariners vs Royals best bet is Under 8.5 total runs in this game. Make sure to find the best odds by checking our live MLB odds page.
Mariners vs Royals Odds
| Mariners Odds | ||
|---|---|---|
| Spread | Total | Moneyline |
-1.5 +122 | 8.5 -115o / -105u | -142 |
| Royals Odds | ||
|---|---|---|
| Spread | Total | Moneyline |
+1.5 -146 | 8.5 -115o / -105u | +120 |
- Mariners vs Royals moneyline: Mariners -142, Royals +120
- Mariners vs Royals over/under: 8.5 (-115o / -105u)
- Mariners vs Royals spread: Mariners -1.5 (+122), Royals +1.5 (-146)
Mariners vs Royals Probable Pitchers
| RHP George Kirby (SEA) | Stat | RHP Stephen Kolek (KC) |
|---|---|---|
| 5-3 | W-L | 2-0 |
| 1.1 | fWAR (FanGraphs) | 0.1 |
| 3.45 / 3.20 | ERA / xERA | 4.24 / 3.99 |
| 3.54 / 3.57 | FIP / xFIP | 4.86 / 3.72 |
| 14.3 | K-BB% | 11.6 |
| 55.2 | GB% | 50.0 |
| .297 | BABIP | .204 |
| 101 | Stuff+ | 89 |
| 113 | Location+ | 114 |
Mariners vs Royals Game Preview
Seattle Mariners Betting Preview
The Mariners are firmly in the hunt for first place in the AL West — the weakest division in baseball. Even with a 25-27 record, they sit just a series behind the Athletics for first place.
George Kirby, who'll draw the start on Saturday, is responsible for five of Seattle's 25 wins. He boasts a solid 3.45 ERA with a 3.21 xERA and a 3.55 FIP.
Those numbers come with a totally different identity. He has a career-low K/9 (7.47) and BB/9 (2.30), but he also sports a 55% ground ball rate — 11% higher than last season. The only substantial change in Kirby's pitch mix is that he's throwing a changeup to lefties 13% of the time, compared to 3% last year.
Although Cal Raleigh struggled and is now on the injured list, Seattle is 10th in MLB with a 100 wRC+ this month. Even if the Mariners' bats struggle, they drive up starters' pitch counts with their 24% strikeout rate and 10% walk rate.
I'd come close to calling the Mariners a "home run or bust" team. A team that relies on the three true outcomes more than most ballclubs. I talked about their strikeout and walk rates, but they hit .211, which is bottom-five in MLB, and have 24 homers, which is fifth.
The trio of Julio Rodriguez, JP Crawford and Randy Arozarena has 13 of Seattle's 24 homers in May. All three also boast a wRC+ better than 120, with Arozarena's 172 leading the way.
Seattle also injected some energy with top-five prospect Colt Emerson joining the team. He's struggled so far, hitting below .100, but tagged a homer for his first hit.
Kansas City Royals Betting Preview
There's no sugarcoating it: The Royals have been terrible in 2026. They lost nine of their past 10 games
On the mound is Stephen Kolek, who is pitching to a 4.24 ERA with a 4.00 xERA and a 4.87 FIP in three starts.
Nothing about Kolek will blow hitters away. He wants to induce contact and keep teams on the ground, as his GB% sits at 50%. The concerning thing for Kolek is his HR/9 which is up to 1.52 in a limited sample. In his 19 starts last year, his HR/9 was a strong 0.72
Kolek is getting barrelled more this year than last year, but with such a high ground ball rate, I expect his home run numbers to level out.
Pitching hasn't been the primary issue for the Royals; it's been the offense. They're 22nd in wRC+ this year with a 93 wRC+, and Bobby Witt Jr. is the only player with a wRC+ above 108.
Salvador Perez looks to be on the downswing of his career, and Vinnie Pasquantino has a 68 wRC+. Those are two of the big boppers that are supposed to bring Witt Jr. in to score. Instead, they're just leaving runners on base, and Kansas City continues to struggle scoring.
Mariners vs Royals Pick, Betting Analysis
I'm rolling with the under here.
Kolek will probably give up a few runs, but Kaufmann Stadium is good at keeping the ball in the yard. That should help his home run issues.
I just don't see this porous Royals offense scoring on Kirby.
How about this? Kansas City scored three or fewer runs in FIVE STRAIGHT games. That seems unlikely to change against a pitcher of Kirby's caliber.
Pick: Under 8.5 (-105, FanDuel | Play to -8)
