In Napoli's absence, Brock Holt slid over from second base to first base and Marrero trotted on the field for the first time to man second.
"It was awesome," said Marrero, the No. 9 Red Sox prospect according to MLB.com. "It was a lot of fun to go in there and grind through that game and try and help the squad."
At the plate, Marrero struck out twice in his two at-bats, but in the eighth, he certainly did his part to aid in Boston's series-clinching victory.
With two away and Logan Forsythe on second, Brandon Guyer shot a ground ball to the right side of the infield that seemed destined for right field, but Marrero ranged to his right, made a diving stop and got the speedy Guyer at first to end the inning and preserve the two-run lead.
"I just try to stay ready every pitch," Marrero said. "He made a good swing and the guy was definitely going to score, so I just laid out to give my relief pitcher a chance and it worked out."
The play is one that Red Sox starter Justin Masterson, who tossed five innings of one-run ball en route to a victory in his return to the rotation, got accustomed to seeing from Marrero during the righty's rehab stint at Triple-A Pawtucket.
"That's why he is here," Masterson said. "He probably didn't hit as well as he would've liked, but that play, that's who he is. I remember when I went down [to Triple-A], he made a play on a ball that I thought was going to be a hit, then he got to it and I thought it would only be one out, and then we turn the double play, and that's what he brings to the table.
"He's a smart guy and he's going to do some great things."
Troy Provost-Heron is an associate reporter for MLB.com. This story was not subject to the approval of Major League Baseball or its clubs.