This time, the catwalks that ring the dome’s ceiling were to blame. One of them stopped a long drive by Rays slugger Nelson Cruz in the third inning of the ALDS Game 1 between Tampa Bay and Boston.

The “C” catwalk (there are four catwalks, labeled A, B, C and D) took the blow. The ball was headed for the left-field seats but caromed back toward the infield instead. Statcast estimated that Cruz’s blast would have traveled 406 feet, well beyond the wall.

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Cruz wasn’t sure what to do, so he kept sprinting until he got the home run signal.

“I had no clue what was going on. I was watching the outfielders. I was, like, what happened? Just thank God it was a homer,” Cruz said after Tampa Bay’s 5-0 victory. The home run was the 18th of his playoff career, tying him with Mickey Mantle, Reggie Jackson and Jose Altuve for sixth-most all time.

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What, exactly, are the ground rules for Tropicana Field’s circus rings, er catwalks? Here’s a quick primer:

What are the ground rules for Tropicana Field’s catwalks?

It’s complicated. A batted ball that hits a catwalk or other objects that are suspended over the field can be ruled a home run, a ball in play, a ground-rule double or a foul ball. A word-for-word rundown from the Rays’ website:

Cruz’s home run Thursday hit the “C” ring.

A visual of how the rings play:

“Obviously that’s always a topic of discussion whenever you’re coming to play here,” said Red Sox infielder Christian Arroyo, a former Ray. “But that’s the ground rules, that’s what they’ve set. It’s part of it.”

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“It threw me off because I thought (Red Sox left fielder Alex Verdugo) was camped under it, and then I saw the ball bounce, and then I saw Nelson Cruz jogging, so I was really, really confused, but, you know, it is what it is,” Arroyo added. 

How many times has a batted ball struck a catwalk for a home run in the postseason?

According to MLB.com, Nelson Cruz is the fifth player to hit a postseason catwalk home run at the Trop. The others:

Evan Longoria, Rays, 2008 ALDS B.J. Upton, Rays, 2008 ALCS Willy Adames, Rays, 2019 ALDS Danny Jansen, Blue Jays, 2020 Wild Card Series