On a day when Doug Fister struck out nine Royals in a row to set an American League record, the Tigers blew a save and rallied on a Prince Fielder infield double and Mike Moustakas' third error of the day.

Once Brayan Pena made a diving stop at first base on Alex Avila's ground ball, Don Kelly dashed in with the winning run, sending the Tigers to a 5-4 walk-off victory on Thursday afternoon at Comerica Park.

The win temporarily stretched Detroit's lead atop the AL Central to a game-and-a-half, pending the White Sox series opener against the Rays Thursday night in Chicago. The Tigers' magic number stands at six.

Thus, just when the Tigers needed to put together a winning streak to recapture command of the AL Central race, they took care of their business by sweeping a four-game series against a team they were expected to beat. It just happened with one of the strangest ninth innings the Tigers have had in a while.

Fister's strikeout streak took him through the first seven innings with a shutout bid, allowing four runs over the first two frames to loom as a formidable margin. Once Moustakas and Jeff Francoeur doubled leading off the eighth, the Royals were back in the game.

It took a ranging play from second baseman Omar Infante to stop the Royals' rally and keep it a one-run game. Once Billy Butler led off the ninth with a game-tying home run off Joaquin Benoit, closing in place of Jose Valverde, the comeback was complete.

The Tigers had managed just two singles since the second inning when Tim Collins took the mound for the ninth. Fielder's leadoff dribbler up the middle didn't look like a hit off the bat, but became one when it skirted under second baseman Johnny Giavotella's glove.

Fielder saw the play, made the turn and took off for second, which looked like an incredibly ill-advised play until shortstop Alcides Escobar threw wide of the bag. It opened up first base for Greg Holland to intentionally walk Delmon Young and set up a double play.

Ramon Santiago tried to bunt the runners over but flinched at a high fastball near his head, bunting back to Collins for the out at third.

Kelvin Herrera entered to face Jhonny Peralta for a second consecutive game and again nearly got a double play. Instead of a takeout slide at second erasing the twin-killing, a Moustakas bobble left everyone safe and loaded the bases with one out.

Avila worked the count full before hitting a sharp ground ball down the first-base line. Pena, the backup catcher who replaced injured Eric Hosmer earlier, made a diving stop and touched first base for the out, but had no chance to catch Kelly running home from third.