In two moves that could make or break the Boston Red Sox World Series hopes, manager John Farrell has reportedly decided to start David Ortiz at first base and Daniel Nava in leftfield for Saturday night’s Game Three in St. Louis.

The moves send Mike Napoli and Jonny Gomes to the bench, with Farrell trying to keep Ortiz’s bat in National League ballpark Busch Stadium, and inserting lefty Nava into the lineup against Cardinals righty starter Joe Kelly.

Ortiz has been on fire in the first two games against the Cardinals, going 4-for-6 with two home runs, and five RBIs, and accounted for Boston’s only two runs in Game Two’s 4-2 loss that evened the series, 1-1.

Napoli has hit 1-for-7 with three RBIs off one double in Game One, and has hit .225 in the postseason. Ortiz played six games at first-base during the regular season, helping turn four double plays, and posting a 1.000 field percentage.

The Cardinals hold all the momentum after rookie sensation Michael Wacha mowed down the most potent offense in baseball in six innings of three hits, two earned runs, and six strikeouts of work.

Aided by a painkilling shot in Game Two, outfielder Carlos Beltran played through a rib injury and sparked the lagging St. Louis lineup with his seventh inning single that brought home Daniel Descalso. That gave reliever Trevor Rosenthal enough run support for three strikeouts in the ninth inning and the save.

Other than Beltran, leftfielder Matt Holliday has eight total bases, with one home run and a .373 average in the series. But as a team, the Cards are hitting .212 with 16 strikeouts to four walks.

The pivotal third game could come down to two pitchers who are still seeking their first win this postseason.

Boston’s Jake Peavy will take the mound in Game Three, with two uneven performances in the previous two rounds. Peavy was tagged for seven earned runs off five hits in a Game Four loss of the ALCS against Detroit, and picked up a no decision against Tampa after 5 2/3 innings and one run surrendered.

The Cards' Kelly has also given up eight earned runs over three starts in October, but has the strikeout edge with 13 compared to Peavy’s four.

Las Vegas Betting Odds: St. Louis-175, St. Louis+1.5

Where To Watch Online: Postseason.TV (International only)

Audio Live Stream: MLB.TV

First Pitch: 8:07 PM Eastern Time 

TV Channel: FOX

Prediction: St. Louis 5, Boston 4