Royals vs. Mariners Prediction, Odds, Probable Pitchers and Prop Bets for Monday, June 30

The Royals have hit the UNDER in 61.5 percent of their games this season.

The Royals are underdogs on the road against Seattle. / Jerome Miron-Imagn Images

The Kansas City Royals and Seattle Mariners open a four-game set on Monday night with Micahel Wacha on the mound for Kansas City against youngster George Kirby.

An All-Star in the 2023 season, Kirby has gotten off to a slow start in 2025 after missing time with an injury. He’s posted a 5.40 ERA in seven starts, and he’s given up more hits (38) than innings pitched (36.2). 

That’s right in line with what Kirby did in 2024, as he allowed more hits than any pitcher in the American League (181). 

Despite that, Seattle is favored at home against a Kansas City team that has dropped seven of its last 10 games. After making the playoffs in 2024, the Royals seem to be facing an uphill battle to repeat that in the 2025 season. 

Wacha (3.33 ERA) has pitched well in 2025, but the Royals are just 8-8 in his 16 outings. Can they turn that around in this series opener?

Here’s a breakdown of the odds, players to bet on in the prop market and my prediction for Monday’s action. 

Royals vs. Mariners Odds, Run Line and Total

Odds via DraftKings Sportsbook.

Run Line 

• Royals +1.5 (-164)
• Mariners -1.5 (+134)

Moneyline

• Royals: +134
• Mariners: -164

Total

• 7.5 (Over -101/Under -120)

Royals vs. Mariners Probable Pitchers

• Kansas City: Michael Wacha (4-7, 3.33 ERA)
• Seattle: George Kirby (1-4, 5.40 ERA)

Royals vs. Mariners How to Watch

• Date: Monday, June 30
• Time: 9:40 p.m. EST
• Venue: T-Mobile Park
• How to Watch (TV): ROOT Sports NW, FDSKC
• Royals record: 39-45
• Mariners record: 43-40

Royals vs. Mariners Best MLB Prop Bets

Royals Best MLB Prop Bet

• Bobby Witt Jr. to Hit a Home Run (+400)

Earlier today, I shared in SI Betting’s best home run picks – Daily Dinger – why this is a great matchup for All-Star shortstop Bobby Witt Jr.: 

Kansas City Royals star Bobby Witt Jr. has a great matchup on Monday night, as he’ll take on the Seattle Mariners and struggling young starter George Kirby.

After missing the start of the season with an injury, Kirby has returned to make seven starts, posting a 5.40 ERA while allowing seven total home runs. The right-hander has also struggled against Witt in his career, even though he has yet to allow a home run to him.

Witt is hitting 4-for-9 (.444) with a pair of doubles against Kirby in his MLB career, posting an OPS of 1.111. 

This season, Witt has 11 home runs, including three over the last two weeks. During that stretch, he’s hitting .320 with a .966 OPS. Plus, all 11 of Witt’s homers this season have come against right-handed pitching.

He’s a great target on the road tonight. 

Royals vs. Mariners Prediction and Pick

After allowing 11 runs over his first two starts this season, Kirby has pitched a lot better in the month of June, posting a 3.54 ERA while leading the Mariners to a 3-2 record.

He still ranks in just the 35th percentile in expected ERA this season, but the Mariners have combined for 7.5 or fewer runs in four or his seven starts.

On the Kansas City side, Wacha has allowed three or fewer earned runs in 13 of his 16 outings in 2025, posting an expected ERA of 3.66. He’s also been the starter in 11 games where the Royals have combined for seven or fewer runs.

The Kansas City offense is the reason I’m taking the UNDER, as no team in MLB has scored fewer runs than the Royals this season. That’s led them to posting the second-best UNDER record in MLB (51-32-1) so far in 2025.

With Kirby starting to settle in after a rough start to 2025, I think this will be a pitcher’s duel on Monday. 

Pick: UNDER 7.5 (-120 at DraftKings)

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Odds refresh periodically and are subject to change.

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