Betts' infield single glanced off the glove of first baseman Chris Davis. After the throw by Davis to the bag got away, Betts briefly contemplated going to second. Once he saw catcher Caleb Joseph backing up the play, Betts scampered and dove back into first, where he was hit on the knee by the throw.
"At first, to the naked eye, it looks like he twisted it on the bag with the slide back in, but it was the ball that hit him in kind of a little bit of a sensitive spot," said Farrell. "But he's good to go."
Betts got up, tested the leg and stayed in the game. Not only that, but just moments later he stole second, as if to prove to everyone he was fine.
Actually, the steal by Betts had a very different purpose.
"I was like, 'I've got to go now before it gets tight,'" said Betts.
Betts then explained how the play unfolded in his eyes.
"I didn't see the catcher, so I was about to try to go to second but saw him come at the last second and the ball just hit me," Betts said. "It just hit in a bad spot. It hurt, it's pretty stiff now, but when I was loose, it wasn't too bad. I'll be all right tomorrow."
The news was good on Betts, but more uncertain for third baseman Marco Hernandez, who exited the game with a left shoulder strain suffered while making an error in the top of the first.
"He's sore right now," said Farrell. "When he went back to field the ball with a drop-step move and the glove hand started to go behind him, he felt like there was a little bit of a slippage sensation that he had. And he's done this before. It was clear we had to get him out of the game. We'll check and see how he comes in tomorrow."
Hernandez has been filling in for starting third baseman Pablo Sandoval, who has a right knee sprain and is on the disabled list. Utility infielder Brock Holt is also on the DL with vertigo.
Farrell didn't rule out Hernandez landing on the DL.
That would leave Josh Rutledge and recently-acquired waiver pickup Chase d'Arnaud as the two players on the roster who can play third base.
Rutledge replaced Hernandez on Wednesday and went 1-for-4 with two RBIs.
Ian Browne has covered the Red Sox for MLB.com since 2002. Follow him on Twitter @IanMBrowne and Facebook. This story was not subject to the approval of Major League Baseball or its clubs.