The A's got a key insurance run on a weird play in the ninth inning of Thursday's 9-8 win over the Royals, when Kansas City third baseman Cheslor Cuthbert's momentum carried him into Oakland's dugout after catching Corban Joseph's foul popup.

Cuthbert made a great grab leaning over the entrance to the visitor's dugout at Kauffman Stadium, but the catch forced him to jump down the dugout stairs. By rule, when a fielder steps or falls into an out-of-play area after making a catch, the ball is dead and all runners are allowed to advance one base.

The A's had Seth Brown on third and Jurickson Profar on second at the time, so Brown came in to score and Profar went to third. Brown's run extended Oakland's lead to 9-7, which proved to be the difference once the Royals rallied for one run in the bottom of the ninth.

"I knew it right away, but you don't see it very often," A's manager Bob Melvin said. "[Third-base umpire Chris Segal] was right on it. That's a huge play, obviously, to get that second run."

Brown said he was aware of the rule, as were the rest of his teammates in the dugout, most of whom immediately pointed to home plate after watching Cuthbert land on their side.

"That was my first one," Brown said when asked if he'd ever scored on a ball caught out of play. "It was really nice, actually."

The relevant section of the MLB rulebook -- Rule 5.06 (b) (3) (C) -- reads, "Each runner, other than the batter, may without liability to be put out, advance one base when: A fielder, after catching a fly ball, steps or falls into any out-of-play area."

Unlike Brown, Cuthbert didn't know about the rule.

"At one point when I was getting close to the ball, I looked down to see where I was at -- if it was going to be a tough play," Cuthbert said. "That's why my first instinct was to hold onto the railing to not fall into the dugout. When the ball was coming down, that's the only shot I had.

"Then the umpire said the runners were going to advance a base. I didn't know about that rule. Every day you learn something in baseball."

Royals manager Ned Yost said even if Cuthbert knew the rule, there's not much a fielder can do.

"That's not a play [where the ball] goes up and you stop and think about your options, like, 'Um, do I let it fall? Do I catch it and go in?'" Yost said. "It's an instinctual play. You try to catch the ball. He caught the ball. He tried everything he could to hold himself back. But that's the way things go for us. ¡­ It couldn't have been a foot one way or the other. He just went right in the dugout."