PHOENIX -- The D-backs' season is on the brink.

Following a 6-1 loss to the Phillies in Game 5 of the National League Championship Series on Saturday, the D-backs trail in the best-of-seven series, 3-2, with Game 6 set for Monday night in Philadelphia.

Merrill Kelly will be on the mound, and if the D-backs win, they force a decisive Game 7 on Tuesday night. If they lose, their season, which included a magical underdog run through the postseason, comes to an end.

Teams ahead 3-2 in any best-of-seven postseason series have gone on to win 79 of 112 times (71%).

The Phillies have won all six games, including the first two of the series, that they’ve played at Citizens Bank Park this postseason to move to 28-11 in home playoff games since the team began playing there in 2004. That’s a .718 win percentage -- the best by any team in any stadium in postseason history (minimum 20 games).

“We know what's ahead of us,” D-backs manager Torey Lovullo said. “We have to go out and play our best game in Game 6. We have a very tough pitcher [Aaron Nola] that we're going to be facing, but once again, I'm going to put it on our group. I believe in Merrill Kelly. I believe in the guys to go out there and execute and play at a higher level and make plays and do things right.”

After winning Games 3 and 4 at home, the D-backs hoped to ride the momentum and a sellout crowd at Chase Field to one more home win.

Instead, the Phillies scored a pair of runs off Zac Gallen in the first inning and got a pair of solo homers from Kyle Schwarber and Bryce Harper off the righty in the sixth. Meanwhile, the D-backs offense struggled to do anything against Philadelphia ace Zack Wheeler.

• Gallen stung by HRs again in all-too-familiar G5 loss

It was the second time that Wheeler had shut down Arizona’s offense. In the Phillies' Game 1 win, he allowed two runs over six innings. This time, it was one run over seven.

“I think he was locating well but at the same time, I don't think we were stringing at-bats together and we just didn't get things rolling, and he was rolling,” said D-backs outfielder Alek Thomas, who homered off Wheeler in the seventh, his second straight game with a long ball. “That's twice that's happened and you know that that can't happen on the biggest stage. So definitely need to do a better job against Nola.”

The D-backs will need to have more grinding at-bats against Nola in Game 6. If they can run the right-hander’s pitch count up, perhaps they can pounce on Philadelphia’s bullpen, which struggled in Games 3 and 4.

By the same token, Kelly will need to keep the ball in the ballpark, something Arizona pitchers and the two other teams the Phillies have faced this postseason -- the Marlins and Braves -- have had a hard time doing.

The Phillies smacked another three homers in Game 5, giving them 23 homers in 11 games this postseason, which is one shy of the 11-game mark set by the Astros in 2004.

The D-backs also need to play a cleaner game. In their Game 2 loss, they had a popup drop amidst three players in the infield, and outfielder Lourdes Gurriel Jr. forgot how many outs there were on a sacrifice fly.

In Game 5, the D-backs did not execute when the Phillies attempted a double steal in the first inning. That cost them a run.

The D-backs have had stretches in which they’ve struggled this year and been able to rebound. They played meaningful games for the last month and a half of the regular season that they may have considered as must-win, but Game 6 will be the only true must-win game they’ve faced.

“We've got to give it our best shot,” Thomas said. “We've got to rally together and find a way to win a ballgame. And just take it one step at a time, one day at a time, and one at-bat at a time, too. We’ve got to believe in ourselves and try to get this thing done.”

After watching the D-backs beat them in Games 3 and 4, the Phillies certainly won’t make the mistake of taking Arizona lightly in Game 6. 

“Winning a game here is huge,” Phillies manager Rob Thomson said. “It really is. Especially how we lost the first two here. It just shows the toughness of our club, the resiliency of our club, because they're not going to quit. They're not. So this thing is not over. We have to show up on Monday and put the pedal down and get after this thing and play good baseball. We really played well tonight.”