Gambling911.com has the Red Sox vs. Guardians game being postponed Friday night at a greater than 90% chance. If you place you bet, it is important to understand a sportsbook's rules pertaining to suspended and postponed games, some of which differ across the board.

Remember that forecasts are subject to change. 

General Rules Pertaining to Types of Bets

If the game is postponed before it begins and is not played within 48 hours of the original start time, all bets are voided, and your stake is refunded at most online sportsbooks.

If the game starts but is suspended and not completed within 48 hours, bets are voided unless the outcome of a specific market has already been determined at most online sportsbooks.

Impacts on Types of Bets

• Single Bets: These are voided if the game isn't completed within the 48-hour window, and your stake is returned.​
• Parlay Bets: If one leg of your parlay is voided due to a postponed game, that leg is removed, and the parlay continues with the remaining selections. The odds and potential payout are adjusted accordingly.
• Player Props: These require all listed players to be active. If a player doesn't participate, the bet is voided.

Totals

If the game goes at least 9 innings (or 8.5 if the home team is winning), the total bet is counted and will be graded accordingly based on the score at the time of suspension.

Should the game be called off prior to 8.5 innings (or 9 full innings if the visiting team is ahead), the total bet is voided at most books. It will therefore be marked as "no action" and refunded in most cases.

In the event of a game suspension that resumes the next day (or within 24 hours), the game is deemed as "unofficial" as it applies to totals bets.  Therefore, they are voided.  However, some books do treat suspensions when resumed the next day differently in regard to totals so it is important to check individual sportsbook rules.

Red Sox vs. Guardians Game Washout

This one is likely to be postponed well in advance of game time, though that hadn't happened as of Friday morning. 

Rain chances were greater than 80% right up through the 11 pm hour.

This was the 10th most wagered on MLB game as of Friday morning.  Gamblers were likely holding back in anticipation of a postponement.