Quick answer: A block in basketball is when a defender legally deflects a shot attempt before it reaches its highest arc. The shot has to be on its way up. Slapping a shot on its way down is goaltending, which is a violation, not a block. Blocks count as both a defensive stat for the player and a missed field goal for the shooter, with the rebound scenario depending on who recovers.
The Mechanics That Get Calls Reversed
The shot has to be ascending. Once the ball reaches its peak and starts coming down, any contact is goaltending and the basket is awarded to the shooter. Officials get this wrong more than they should, and replay review has reversed dozens of high-profile blocks back into goaltending calls. The other tricky scenario: blocks on layups when the ball has already touched the rim or backboard. Once the ball touches either, it’s a rebound situation, not a block opportunity.
Blocks Props on the NBA Slate
Block props are typically priced at half numbers (Victor Wembanyama over 2.5 blocks). The variance on this market is brutal. Even Wemby has nights with zero. The line tends to sit at 1.5 for elite shot blockers and 0.5 for most starters. Books charge serious vig on these (often -130 over and -110 under) because the binary nature of the underlying outcome makes pricing hard. Public money piles on overs for star defenders, which is why under bets at -110 sometimes carry actual value when the matchup is neutral.
The Sharp Edge
Blocks correlate with opponent shot selection more than any single defender’s ability. A team with elite drive-and-kick offense generates fewer blockable shots because the second-look kickout often goes for a three. A team with a slasher-heavy offense (Memphis Grizzlies, Sacramento Kings) creates more rim attempts and inflates block opportunities. PropsBot’s calibration model bakes opponent shot profile into the projection, which is part of how the High ROI Signal hits 31.7% verified ROI across our most-tested sport.
Records and Per-Game Reality
Hakeem Olajuwon owns the career blocks record at 3,830. Single-season record belongs to Mark Eaton at 5.6 blocks per game in 1984-85. Single-game record is 17 by Elmore Smith in 1973. Modern stars sit in the 2 to 3.5 per game range during peak seasons. A consistent 2-blocks-per-game player is rare enough to anchor a team’s defensive identity.
Frequently Asked Questions
What counts as a block in basketball?
A legal deflection of a shot attempt while the ball is still on its way up. The defender must contact the ball, not just the shooter’s hand or arm. Otherwise it’s a foul.
What’s the difference between a block and goaltending?
Timing. A block hits the ball before it reaches the peak of its arc. Goaltending hits the ball after the peak (or after it’s already touched the rim or backboard). Goaltending is a violation; blocks are legal.
Are blocks props worth betting?
Only with a model that accounts for opponent shot profile. The variance is too high for gut feel. Vig is also higher on blocks props than on most NBA markets.
Who has the most blocks in NBA history?
Hakeem Olajuwon with 3,830 career blocks. The stat wasn’t tracked officially until the 1973-74 season, so older big men like Bill Russell don’t have official totals.
Do blocks count if the ball still goes in?
No. A block requires the shot to miss as a result of the deflection. If the ball goes in despite the contact, it’s a made basket, not a block. The defender is credited with nothing.
Part of the PropsBot.AI Sports Betting Glossary. Updated 2026-05-04.
