With the contest tied at one heading into the bottom of the 10th, third baseman Chad Flack drew a leadoff walk from FSU starter Elih Villanueva (4-2) to start the series-clinching rally. Seager roped a 2-0 pitch from reliever John Gast down the right field line to put runners on the corners, and catcher Tim Federowicz was intentionally walked to bring up designated hitter Mark Fleury with the bases loaded and no outs.
Fleury needed to see just four pitches from Gast to drive in the game-winning run with a walk-off base on balls.
The victory lifted the Tar Heels to a series win in a much-anticipated three-game set featuring two of the nation's top three ranked teams. UNC is now 7-3 against nationally-ranked teams this season and has won its last four home series with the Seminoles.
Right-hander Rob Wooten (3-1) picked up his second win over the weekend with two shutout innings out of the bullpen. Villanueva pitched into the 10th and held the Tar Heels to just two runs on two hits and a walk but took the tough-luck loss. He struck out three and was relieved by Gast after issuing the leadoff walk to Flack in the 10th inning.
After the teams combined for 30 hits in Saturday's game, FSU and UNC tallied only seven base hits in the finale. Seager, who was 2-for-4, was the only player with more than one hit in the contest.
The Tar Heels allowed a season-high 19 hits in Saturday's loss, but bounced back to close the series in strong fashion on the mound. Right-hander Matt Harvey struck out five and held FSU to just one unearned run on one hit over 4 2/3 innings. He left with two on in the fifth after issuing two of his career-high six walks. Lefty Brian Moran picked up the final out in the fifth and worked a career-long 3 1/3 shutout innings to keep Carolina in the game.
UNC also matched a season high with four double plays on the afternoon.
In the third, a two-base throwing error by shortstop Garrett Gore on a Mike McGee chopper put a runner in scoring position, and Stephen Cardullo followed with a double down the right field line to put the Seminoles on the board. Harvey followed with back-to-back walks to load the bases, but Buster Posey hit into a 4-6-3 double play to end the inning.
Carolina finally got its first base runner in the fifth on a throwing error by FSU shortstop Tony Delmonico, but Villanueva used an inning-ending double play to face the minimum through five innings.
Ackley finally broke up the no-hit bid in the seventh with a leadoff single through the right side. Ackley was retired when left fielder Kyle Shelton bunted into a fielder's choice, but Flack was a hit by a pitch to give the Tar Heels' their first runner in scoring position on the afternoon. Seager then delivered the tying run with a two-out single to left center for his ACC-best 63rd RBI.
Florida State immediately threatened with runners on the corners thanks to back-to-back one-out singles in the eighth, but the Tar Heels were able to turn their third double play of the game to preserve the tie. Carolina also pitched out of a jam in the ninth when Gore's third error of the afternoon put two runners on, but Wooten induced a pair of fly ball outs to keep FSU off the board.
Carolina's six seniors - Flack, Wooten, Shelton, Mike Facchinei, Tyler Trice and Seth Williams - were honored during Senior Day ceremonies prior to Sunday's game. This group has accounted for 190 wins over the last four seasons. Flack played in his 245th career game Sunday to eclipse Chad Prosser's previous school record of 244.
The Tar Heels will break for final exams and are back in action Tuesday, May 6 to open a two-game series with North Florida.