Is Mason Miller Actually Eligible to Win American League Rookie of the Year?

The American League Rookie of the Year market has been without a true No. 1 for most of this season, but we're now discovering the real favorite has been under our nose the entire time, and he wasn't even listed at our best sports betting sites.

The betting story that's completely consumed my mind (and my activity on X) for the past three days is whether Oakland Athletics phenom closer Mason Miller is actually eligible to win the American League Rookie of the Year Award.

It started on May 8 when FanDuel listed Miller as the favorite, ahead of Baltimore Orioles outfielder Colton Cowser.

As I noted in our look at the MLB Rookie of the Year odds, FanGraphs considers Miller a rookie in all of its leaderboards. However, Baseball Reference explicitly states Miller "exceeded rookie limits during (the) 2023 season." So, what gives?

Well, I went on a little deep dive so you don't have to, and we're getting to the bottom of Miller's AL Rookie of the Year eligibility, with odds from our best MLB betting sites.

Mason Miller's 1st appearance in AL Rookie of the Year odds market

We've been following the Rookie of the Year odds since the offseason. We tracked and updated them through spring training and have updated them multiple times per week during the regular season.

Before FanDuel added him on May 8, I saw Miller listed at just one of our best sports betting apps, for one day in April.

On April 17, bet365 listed Miller in its AL Rookie of the Year market at +6500, priced among many rookies who've yet to play this season. At that point, though, he already appeared to be one of baseball's more dominant relief arms.

By that date, Miller had made six appearances - making his seventh that evening - and racked up three saves. He had 15 strikeouts over just eight innings, owning a 2.25 ERA and a truly elite 0.53 FIP.

The betting favorite to win AL Rookie of the Year on April 17 was Cowser, with Texas Rangers outfielder Evan Carter more or less the co-favorite.

For his part, Carter owned just a .211/.338/.404 slash line with two home runs. Carter's teammate, Wyatt Langford, was the third-biggest favorite, and he had yet to hit a home run and owned an abysmal .646 OPS.

This is all to say, if Miller was to be properly listed in the AL Rookie of the Year market at our best sportsbooks on April 17, he likely should have been trading at a price around +500, similar to that of Jackson Holliday, whom the Orioles called up a week prior.

Starts popping up at more sportsbooks

That brings us to May 8, when Miller made his first "real" appearance at any of our sites with the best sportsbook promos.

FanDuel listed him just ahead of Cowser as the favorite, who was trading at +220. The question then was, why were we just seeing Miller pop up in the second week of May when he had been widely discussed as one of baseball's most dominant relievers - not rookie relievers, all relievers - for weeks?

That's when I took to X in search of some answers, after seeing the likes of MLB.com's Mike Petriello - a writer whom I respect and trust - note that Miller is, indeed, a rookie.

Is Miller actually a rookie?

After doing some digging, I can say with at least some confidence - despite what Baseball Reference states - that Miller is eligible to win AL Rookie of the Year. 

MLB's rookie eligibility rules are as follows:

A player shall be considered a rookie unless he has exceeded any of the following thresholds in a previous season (or seasons):

• 130 at-bats or 50 innings pitched in the major leagues.
• 45 total days on an active major league roster during the championship season (excluding time on the injured list).

The confusion seems to stem from whether Miller exceeded those 45 days on the Athletics' roster, since he pitched only 33 1/3 innings. Here's a brief timeline of his 2023 season:

• Debuted on April 19
• Last pitched on May 7 before suffering an injury (19 days of service time)
• Athletics place him on the injured list on May 11, retroactive to May 8
• Athletics reinstate him from the injured list on Sept. 6
• Makes final appearance of season on Oct. 1 (26 days of service time)

The issue, then, is whether May 8 counts as a day Miller spent on the active roster.

If it's ruled that Miller hit the IL on May 8 at midnight, meaning he didn't spend any part of that day on the active roster, then he spent exactly 45 days in the majors last year, making him a rookie in 2024.

However, I operated under the assumption that he was both active and inactive on May 8, leaving him ineligible with 46 days. I imagine Baseball Reference is using that same criteria with its ruling, but it appears the debate has been put to rest.

How to approach Miller in the AL Rookie of the Year betting market

Another one of our best live betting sites added Miller to its AL Rookie of the Year market on May 9. Caesars listed Miller just behind Cowser, priced at +250.

Since opening, FanDuel shortened Miller's odds to +195 with Cowser now at +295, while Caesars lengthened Miller's odds to +275.

Mason Miller AL Rookie of the Year odds

(Odds as of May 10)

None of our other best sportsbooks have yet to follow suit, with Shane Jackson of BetMGM telling me its trading team is still waiting for clarification on Miller's status before it adjusts its offerings.

My advice is the same as I'd give for any other daily or futures bet: provide yourself with the opportunity to find the best price.

Caesars' +275 odds are enticing, and I'd go as far as to say they're too long. Miller hasn't just been the best AL rookie to date, but he's also been the most talked-about. He could justifiably be trading at a price close to +150, just as Mookie Betts is in the MLB MVP odds.

However, what if DraftKings, BetMGM, or bet365 list Miller at around +300 or longer due to his well-documented injury history and the potential risk he's traded this season?

FanDuel set the market and Caesars already went longer, so who's to say another sportsbook won't take that one step further?

Futures advice: read the fine print

One thing I'll note as a lesson from all of this is to always check the language used by whichever sportsbook you're betting at.

If you look at FanDuel's MVP and Cy Young markets (as of May 10), you'll see that it says "Other selections available on request" above the players listed.

Interestingly (and I don't know when they added this, so it's not meant to sound accusatory in any way), FanDuel added "All bets are action" ahead of the aforementioned line for its Rookie of the Year markets. That means, if you bet on Miller and we found out he was ineligible, it's unlikely your bet would have been void at FanDuel.

Similarly, Caesars has since added that same "All bets are action" line to its Rookie of the Year market, though it's also noticeably absent from MVP and Cy Young.

As far as I can tell, none of our best sportsbooks that don't offer Miller as a Rookie of the Year option make such a distinction.

On the flip side, I'll say that sometimes, if a price looks a little too good to be true, you may just want to slap a few dollars on it. At least, that's how I feel now when I look back at those +6500 odds at bet365 on April 17.

Additionally, if you do pay attention to the language used by said sportsbook and there's nothing to suggest your bet won't be void, then you can really drop the hammer with a normal-sized wager.

If you're looking for more futures advice, be sure to check out my feature on why it's time to stop betting on Mike Trout to win AL MVP.

Here are our best MLB betting sites:

• Caesars Promo Code: SBRBONUS1000 | Read our Caesars Review
• BetMGM Bonus Code: SBRBONUS | Read our BetMGM Review
• bet365 Bonus Code: SBRBONUS | Read our bet365 Review
• BetRivers Promo Code: SBRBONUS | Read our BetRivers Review
• FanDuel Promo Code | Read our FanDuel Review
• DraftKings Promo Code | Read our DraftKings Review

(21+. Gambling Problem? Call 1-800-GAMBLER)
* Bonuses not applicable in Ontario.

Related pages

• Best Sports Betting Sites | Best Sportsbook Promos (U.S. only)