I use Gametime. Literally stand in front of the stadium and watch prices drop, but 10 min before first pitch. Works great for weeknight games, but you might want to buy ahead for weekends in Boston.

I like TickPick for resale tickets.

Thanks for your reply. Not at all picky about seats, just looking at options for low cost bleachers. I'd be bringing my 6yo to his first game so we are unlikely to even stay the entire time

And honestly no clue on division rankings and such and impact on sales, other than knowing Fenway tends to be a busier park even if they're having a poorer season.

I presume scanning SeatGeek the day before once we have a better sense of weather may be the way to go. Just did not know if there were other ticket sites that would be worth checking out than ones like SeatGeek, StubHub, Ticketmaster, VividSeats, etc. for a last minute type of thing. Rarely get out to special events like these!

How picky are you about where you sit and is this game going to be important for standings?

The Sox being second in their division, it being later in the season, and it being a weekend do make it slightly more likely this sells out. Looking at attendance, Fenway isn't selling out but it's averaging okay. But if you're not picky about seats or willing to do standing room you could chance walking up to the box office.

How have their sales been on weekends recently?

I'll be in Boston for the weekend later this month and am looking at Red Sox tickets in the bleachers. There are plenty available on the resale sites, but I haven't actually used those before.

I want to make a (literal) game day decision to get tix to make sure the game is not rained out. Tickets are a splurge for me and I won't be in town to attend a rain date game if it gets rescheduled.

Is there a better site to use same day for tickets people will unload as the game time approaches?