"Might be a play that only Rodriguez can make," Pirates manager Clint Hurdle said.
Rodriguez entered the game in the eighth inning as a defensive replacement for Pedro Alvarez. It's a role he's served many times this year, as he's played in 62 games at first but only started 12.
Starter Gerrit Cole's strong start came to an end with two outs in the inning, after he allowed two singles. In came lefty reliever Tony Watson to face Harper, one of the most dangerous hitters in baseball.
Harper swatted a 95-mph sinker from Watson to the right side of the infield. Second baseman Neil Walker had a chance at the ball, if he timed his dive right. But Rodriguez got to it first, sliding to his right and making a tough backhanded grab.
Rodriguez quickly spun and threw the ball toward first base, where Watson sprinted over just in time to beat Harper.
"He's always ready," Walker said. "He knows his role on this team. He knows what he's going to be asked to do. Nothing ever surprises him -- especially on the defensive end. ... He always seems to be where he's supposed to be."
As easy as Rodriguez often makes it look, it's important to remember he's not a natural first baseman. Rodriguez came up through the Angels' system as a middle infielder. He started working as an occasional spot starter at first base with the Rays in 2013.
Now, his primary role with the Pirates is that of a defensive-minded first baseman, occasionally just for an inning or two at a time. As he showed again on Sunday, he's learned to handle that assignment as well as anyone.
"I guess, in a prideful sense, I hope I'm making plays no one can make," Rodriguez said. "I'm a middle infielder playing first base. I'm definitely comfortable."
Adam Berry is a reporter for MLB.com. Follow him on Twitter at @adamdberry. This story was not subject to the approval of Major League Baseball or its clubs.