Ordinarily, the Red Sox would have had the Cincinnati Reds exactly where they wanted them, which is to say trailing by two runs in the eighth inning with set-up man Junichi Tazawa jogging in from the bullpen and closer Koji Uehara warming up behind him.

But nothing about this season has gone according to the plan.

And so, Tazawa allowed two runs in the eighth, Uehara looked as mortal as every other closer in white-knuckling his way through the ninth, and a potential bottom-of-the-ninth rally fizzled when Mike Napoli grounded weakly to shortstop with the winning run on third base.

It wasn’t until three innings, and nearly one hour, later that Grady Sizemore ended a 4-hour, 4-minute marathon by lifting a single to the Wall that scored David Ortiz for a 4-3 victory, the Red Sox’ second walkoff win at Fenway Park after notching 11 of them last year.

Sizemore’s hit against Reds reliever Logan Ondrusek was only the Sox’ second hit in 13 at-bats with runners in scoring position. Over the past six games, they are 11-for-57 with runners on second or third base and have left 53 men on base.

But all’s well that ends well, and Sizemore made sure that it ended well. After very nearly signing with the Reds in the offseason, he finished with three hits, including an RBI single in the third inning that opened a 3-1 lead.

Armed with that lead, Tazawa got in trouble after issuing a one-out walk to Joey Votto. Brandon Phillips followed with a double before Todd Frazier lined an RBI single into left field to cut the margin to 3-2. Ryan Ludwick tied the game with a sacrifice fly to right.

If Uehara had given up the go-ahead run, he’d have had no one to blame but himself. He failed to cover first on a leadoff single by Zack Cozart, who went to second on a sacrifice bunt, then he gave up a long fly ball that Shane Victorino tracked down in right field and a bunt single to Chris Heisey before finally getting Votto to pop out.

The Sox were positioned to win it in the ninth, even after Dustin Pedroia was caught stealing second base. Victorino and Ortiz worked two-out walks against Sam LeCure, and after Victorino stole third, Napoli grounded out.

In 2014, nothing comes easy to the Red Sox.