BOSTON — Pick a word. Incredible, maybe? That’s as good as any.

Tony Abreu’s two-out RBI single in the 12th inning Saturday night lifted the Royals to an improbable 10-9 victory over the Boston Red Sox at Fenway Park.

The Royals blew an early three-run lead and later erased a six-run deficit. They also escaped a first-and-third threat in the Boston 10th when catcher Salvy Perez made a terrific sweep tag at the plate.

“When I made that play,” Perez said, “I thought, `OK, we have to win this game.”

Both teams burned through their bullpens in this 4-hour, 31-minute marathon, and the Royals, fittingly, scored the winning run with a two-out rally — all six of their runs in the seventh came with two outs.

Boston reliever Junichi Tazawa, 0-1, walked Jeff Francoeur before Eric Hosmer drove a double to left. Tazawa then jumped ahead 0-2 on Abreu before Abreu slapped an RBI single to left.

“I went to the plate wanting to make good contact,” Abreu said. “He made a mistake and left a pitch up. I wasn’t trying to do too much. It happens.”

After that, it was just a matter of Greg Holland closing out a victory for Francisley Bueno. Holland did just that for his seventh save in seven chances since becoming the club’s closer.

Bueno, 1-0, got the ritualistic beer-and-baby-powder shower afterward in recognition of his first major-league victory.

“I’m very happy,” Bueno said, “because everybody showed their excitement about my win. It was fun for us to celebrate our victory.”

The Royals overcame a six-run deficit for the first time since Sept. 21, 2009, when they trailed Boston 6-0 and 8-2 at Kauffman Stadium before rallying to win 12-9. They also won for the third time in franchise history when surrendering 20 or more hits.

Both of those games also went extra innings: a 14-13 victory at Minnesota in 12 innings on Sept. 29, 1970; and a 13-12 victory in 10 innings at home against Cleveland on July 21, 2002.

About that Boston 10th …

Pedro Ciriaco led off with a single through the right side against Kelvin Herrera. Recall that it was Ciraco’s bloop two-run double Friday against Herrera that lifted the Red Sox to a 4-3 victory in the series opener.

Herrera then bounced a wild pitch past Perez, which moved Ciriaco to second. Ciriaco took third on Scott Podsednik’s sacrifice. The Royals chose to walk Dustin Pedroia before summoning Bueno to face Jacoby Ellsbury.

It was a percentage lefty-on-lefty move in a low-percentage situation.

“I was trying to get a strikeout,” Bueno said, “or an infield ground ball. The infield was in, and that gave us a chance (for a play at the plate).

That’s what happened.

Hosmer fielded Ellsbury’s sharp grounder to first and threw home, and Perez applied a sweep tag in a bang-bang play for the out.

“It was a little bit of a high throw,” Perez said, “but (Ciriaco) was right in the line. If he’d gone behind me a little, it would have been hard for me. But he came right to me.”

Bueno ended the inning by striking out Che-Hsuan Lin.

The Royals also had a chance in the 10th inning. Mike Moustakas, whose two-run triple capped a six-run seventh inning, reached as the leadoff hitter when hit by an 0-2 pitch from Vicente Padilla.

Moustakas took second on Francoeur’s grounder to first, which prompted an intentional walk to Hosmer. The threat fizzled when Abreu and Lorenzo Cain struck out.

Abreu later atoned.

“It was a totally different at-bat,” Abreu said. “Padilla was throwing some pitches that I didn’t see well. I was looking for one pitch, but it was hard for me to get it. But I had the opportunity to redeem myself.”

It was all a remarkable roller-coaster ride.

The Royals built a 3-0 lead against Boston starter Aaron Cook just four batters into the game but saw the Red Sox batter Jeremy Guthrie for seven runs in 2 2/3 innings. When Everett Teaford allowed two more runs in the fourth, the Royals trailed 9-3.

“I wasn’t sharp tonight,” Guthrie said. “I didn’t execute too many pitches. When I missed down, I was way down. And when I was up, I was up (in the) middle.”

It was still 9-3 with two outs in the seventh when the Royals erupted for six runs against three Boston relievers and pulled even at 9-9.

That permitted Guthrie to escape with a no-decision, which is probably fair since he got a no-decision in his last start after, on review, carrying a no-hitter into the eighth inning against the White Sox. Cook drew the start on three days of rest, instead of the usual four, in place of Josh Beckett, who went to the Dodgers in the nine-player megadeal that was confirmed earlier in the day. All-Star first baseman Adrian Gonzalez also departed in that trade.

The Royals opened the game with singles by Jarrod Dyson and Alcides Escobar, a two-run double by Alex Gordon and an RBI single from Billy Butler. That quickly, it was 3-0, but the Red Sox battered Guthrie for four runs in the second inning.

Mauro Gomez, playing in place of Gonzalez, rocked a one-out homer over the Green Monster that ended Guthrie’s streak. Jarrod Saltalamacchia and Ryan Lavarnway followed with singles before Mike Aviles cleared the Monster for a three-run homer.

Four straight hits. Four straight runs. Two home runs. Boston led 4-3.

It only got worse.

Guthrie failed to survive a three-run third that pushed the lead to 7-3. Teaford gave up two more runs in the fourth. The Royals, meanwhile, turned turtle against Cook after their early burst.

Cook allowed just three hits, all singles, after Butler’s RBI double before exiting after the sixth. Ah, but the Royals stirred to life against Andrew Miller, who inherited that six-run lead to start the seventh.

Hosmer’s one-out single preceded two-out walks to Dyson and Escobar.

Gordon’s two-run single to right cut the lead to 9-5 and brought Mark Melancon into face Butler with runners at first and third. Butler sliced the first pitch into right for a rulebook double when the ball hopped into the seats.

Perez’s bloop single to right scored Gordon, cut the lead to 9-7, put the tying run on base and prompted another pitching change: Craig Breslow to face Moustakas, who snapped a zero-for-18 drought with a two-run triple to right.

And the game was tied.