David Huzzard: How will Nats construct their postseason roster?

It feels like it has been months that people have been debating who should be on the Nationals' postseason roster. The main focus of the debate has been which starter should go to the bullpen. All I'll say about that is tonight is a big start for Tanner Roark, who has regressed to the mean a bit since the beginning of August pitching 44 1/3 innings to a 3.65 ERA (while, in the same time period, Gio Gonzalez has pitched 40 2/3 innings with a 3.54 ERA).

Not much difference in those numbers, but Gonzalez has swing-and-miss stuff that will play better in the playoffs and a career track record of being a very good starting pitcher; Roark has experience coming out of the bullpen that Gonzalez lacks.

No matter which starter makes the rotation and which is put in the bullpen, the Nationals are going to have an open roster spot and the playoff roster has to be 25 players. That isn't the only open roster spot though. With how Jerry Blevins has pitched recently, it is hard to see him making the postseason roster. The same can be said of Rafael Soriano, and even though Ross Detwiler has looked good in recent outings, they have been few and far between, with manager Matt Williams seemingly avoiding him at all costs.

In the Nats' 14-inning win in Los Angeles, Williams paraded out every September call-up ahead of using Detwiler, who ended up not getting in the game, and two days later when Williams wanted to stay away from the back of his bullpen he used Aaron Barrett and Xavier Cedeno over Detwiler.

Let's also figure that Ryan Zimmerman is back in some capacity. That doesn't take up one of those three open roster spots, as with the addition of Asdrubal Cabrera it is unlikely that the Nationals would need to keep Danny Espinosa on the bench just in case Ian Desmond gets hurt mid-game. With Detwiler, Soriano and Blevins out of the bullpen and a starting pitcher in the bullpen, there are currently five relievers. It would be best to have seven relievers out there and currently Matt Thornton is the only left-hander.

That might not be an issue, as presumably if the Nats are winning the game with the starting pitcher going six innings, and if they didn't, then that second starter was brought in to get through six innings. With Tyler Clippard and Drew Storen having the eighth and ninth, the seventh is the only inning that would require Williams to play matchups. In 2014, left-handed hitters have a .563 OPS against Thornton and right handed hitters, .632. In other words he'd be fine to face one or two right-handed hitters around a lefty.

The Nats don't need a second left-handed pitcher in the bullpen, and if they did, it would have to be Detwiler based on 2014 numbers. But since they don't need one, the 23rd and 24th spots on the playoff roster should go to Aaron Barrett and Blake Treinen. Since returning to the roster as a September call-up, Barrett has yet to allow an earned run and Treinen has looked good in whatever role the Nationals have put him in all season. They are both hard throwers that could make a dangerous bullpen even moreso and the Nats are going to need pitchers in the playoffs that can keep the games close when they're behind.

That takes care of the bullpen, but there is still one open roster spot. That final roster spot should go to a third catcher. Not so much because Jose Lobaton is some great pinch-hitting threat that the Nats need to use late in games, but more because Wilson Ramos is slow - very slow - and if he were to say get a lead-off double in the bottom of the seventh in a tie game in the playoffs, he should be pinch-run for. Having the third catcher allows Williams to make that move and not have to worry about an injury to Lobaton leaving the Nationals with Kevin Frandsen as their emergency catcher in a playoff game.

The Nationals don't need an eight-man bullpen, and they don't have some super hitter that can't play defense from their minor leagues. The best way to take advantage of the final spot on the playoff roster is to use it to maximize late-inning run-scoring opportunities.

David Huzzard blogs about the Nationals at Citizens of Natstown. Follow him on Twitter: @DavidHuzzard. His views appear here as part of MASNsports.com's season-long initiative of welcoming guest bloggers to our pages. All opinions expressed are those of the guest bloggers, who are not employed by MASNsports.com but are just as passionate about their baseball as our regular roster of writers.