September keys for the Nats as the home stretch arrives

And so September has arrived at last and the baseball season has reached the home stretch. If it feels like this has been a long time coming ... well, it has. Think about how much has happened since the Nationals left Viera for the final time and came north to open what most hoped - but weren't certain - would be a promising season.

Things have turned out almost as well as the Nationals could have hoped.

Max Scherzer, Stephen Strasburg and Tanner Roark are among the best pitching trios in baseball (once Strasburg returns from his sore elbow in the next week or two, of course). Daniel Murphy is an MVP candidate, and Wilson Ramos should get some Top-10 votes as well.

Bryce Harper slumped big-time through the summer but has returned in force over the last several weeks. Jayson Werth has still got it at 37, Anthony Rendon is a complete ballplayer again and Trea Turner has seized the everyday leadoff spot and center field job. Mark Melancon has been lights-out since his acquisition from the Pirates, and the bullpen as a whole has the best ERA in the National League.

Sure, Ryan Zimmerman and Danny Espinosa are slumping extensively at the plate, but both guys have provided elite defense. And while the back of the rotation has been beset by injuries (Joe Ross), inconsistencies (Gio Gonzalez) and underwhelming rookies (Lucas Giolito, Reynaldo Lopez) these are relatively minor problem areas most other major league clubs would kill to be their biggest worries.

Above all else, the Nationals enter their weekend series in New York with a commanding lead over both the Mets and Marlins, given overwhelming 99.6 percent odds of winning the division according to Baseball Prospectus and FanGraphs.com.

There are still matters to be resolved, though over the next month. So here are some key factors to watch as the pennant race kicks into high gear at last ...

* The Nats need to get healthy, and soon
Two-fifths of the rotation remains on the DL in the form of Strasburg and Ross, but there has been encouraging news on both fronts. Strasburg has thrown two bullpen sessions this week and reported no problems. He may not need more than another week or so to return to the active rotation. Ross has made two appearances for Triple-A Syracuse, and though he still needs to build his pitch count up, he could do that out of the Nationals bullpen before ultimately returning to the rotation by season's end.

Stephen Drew continues to progress from his inner-ear injury, and after taking full rounds of batting practice and infield drills this week, he began a rehab assignment with Single-A Potomac last night, reaching base three times (double, two walks).

Sammy Solis, on the other hand, remains a question mark in his return from shoulder inflammation. The Nationals would love to have the left-hander back in full force for the stretch run and playoffs, but they've covered their bases by acquiring Marc Rzepczynski (who has pitched well so far).

* September call-ups are on the way
All major league clubs are allowed to expand their rosters up to 40 now that the calendar has shifted to the September. The Nationals won't field 40 active players (no one does) but they will add several more bodies over the next week, with reinforcements coming in a couple of waves based on the club's needs and the final days of the Triple-A and Double-A seasons.

Who figures to be among the call-ups? Look for a couple of veteran pitchers in Mat Latos and Sean Burnett (though the team will have to clear a spot on the 40-man roster for each). Look for previously promoted youngsters like Pedro Severino, Wilmer Difo, Brian Goodwin, Lopez and Giolito to return to the big leagues. And look for some more semi-familiar names we haven't seen so far this year (Trevor Gott, Matt Grace, Rafael Martin) to be in the mix.

* The pressure's on Zimmerman to get right
The Nationals desperately want Zimmerman to be their everyday first baseman come October, and they're going to continue giving him every opportunity to start producing at the plate. But, boy, he doesn't look good right now.

Zimmerman now owns a .217 batting average, .275 on-base percentage and .653 OPS this season, all career lows. He briefly flashed glimpses of production when he returned from the DL and went 4-for-5. But since then, he's 4-for-39 with one double and zero RBIs.

Given the team's comfortable position in the standings, Dusty Baker can afford to keep throwing the 31-year-old out there, hoping he figures it out. But does there come a point when the Nationals can't afford to stick with him?