NRFI MLB today
NRFI (No Run First Inning) is one of the highest-volume MLB markets — every game offers it, and most games actually go NRFI (~55% league-wide). The edge comes from knowing which matchups deviate from average. We project each game's first inning using a Poisson model on the two starting pitchers' ERAs, both lineups' OPS, park factor, and current weather.
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How NRFI is calculated
For each team, expected 1st-inning runs = league baseline (0.52 R/inning) × (opposing pitcher ERA ÷ 4.20) × (team OPS ÷ .720) × park factor × weather multiplier. We then convert each team's expected runs to a Poisson probability of scoring zero (P = e^-λ), and NRFI = P(home scores 0) × P(away scores 0).
v1 limitation: we use full-season ERA, not true 1st-inning splits. Some pitchers are notoriously slow starters (giving up more runs in the 1st than their season ERA suggests). We're working on play-by-play mining to add this in v2.
NRFI factors that move our model
- Ace vs ace: two starters with ERAs < 3.50 = NRFI lean by default.
- Coors / hitter parks: 1st-inning runs are ~15-20% higher at Coors than league average.
- Wind out + warm temp: small but real — adds ~5% to YRFI probability.
- Top-of-order quality: high-OBP leadoff men generate baserunners → more YRFI risk.
Frequently asked
What is NRFI in MLB betting?
NRFI stands for "No Run First Inning" — a bet that neither team scores in the 1st inning. YRFI ("Yes Run First Inning") is the opposite. Sportsbooks offer both sides on every game; pricing is usually NRFI -130 to -150 because NRFI hits ~55-60% of the time league-wide.
How accurate is your NRFI model?
v1 uses full-season pitcher ERA + team OPS + park + weather. Calibration is reasonable but not yet validated over hundreds of games. v2 will mine play-by-play data for true 1st-inning pitcher and team splits — that should add 5-10% accuracy.
What is the best NRFI matchup to bet?
Two starters with sub-3.00 ERAs at a pitcher-friendly park (Oracle, Petco, T-Mobile) in cool weather with wind blowing in. Avoid Coors and hitter parks regardless of ERA.
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