Nats infield returns intact, but there are some questions

As the start of spring training fast approaches, we're breaking down the state of the Nationals roster, position by position. The series continues today with the infield ...

The Nationals return their entire starting infield from last season, and why wouldn't they be excited about that? This quartet featured the first .300-30-100 hitter in club history, the runner-up for the league's batting title, the league's co-leader in WAR and a shortstop who stole 46 bases in 98 games while committing only eight errors.

Can't ask for anything more than that, can you? Well, in this case, the Nats could ask for a little more certainty than they've got in the infield as they prepare to open spring training.

Though he enjoyed his second straight fantastic season at the plate, Daniel Murphy comes to camp still rehabbing from a significant surgery to his right knee. Murphy had a microfracture and debridement procedure in late October and has not yet fully recovered from it. He's not lagging behind in his schedule; it just takes this long to return to 100 percent. The Nats remain hopeful he'll be ready for opening day but they're not going to push it if they feel he's better served delaying his 2018 debut a bit.

Because there aren't many baseball players who have dealt with this surgery - Justin Turner was great after his microfracture surgery, Grady Sizemore was never the same - it's hard to say with any real certainty what the Nats can expect from Murphy this season. But if the 32-year-old second baseman can complete the rehab process with no setbacks, he does remain one of the best pure hitters in the sport. The greater concern may be in the field, where his glove already lagged well behind his bat pre-injury.

There's no injury concern for Ryan Zimmerman, always an encouraging sign for a veteran who has played through and missed time with so many ailments during his career. Zimmerman is hoping to pick up right where he left off last season, when he became the first Nationals player ever to hit .300 with 30 homers and 100 RBIs during a phenomenal bounceback year.

Does Zimmerman, 33, have another one of those in him? That may be too much to ask. His No. 1 priority will be to keep himself healthy and in the lineup, then hope he enjoys enough prolonged hot streaks at the plate to post solid numbers by season's end.

New manager Dave Martinez would be wise to take a page from his predecessor, Dusty Baker, and give Zimmerman regular days off, even when he's feeling and playing well. It helps, of course, to have a strong backup at first base, and for the second straight season it appears the Nats have just that. Despite the loss of professional hitter Adam Lind to free agency, the club got itself a near carbon copy in Matt Adams. The former Cardinals and Braves slugger is four years younger than Lind and boasts similar offensive stats. He'll both make starts at first base against right-handers and serve as the top left-handed bat off the bench.

The surest thing in the Nationals infield is at the hot corner, where Anthony Rendon again proved he is one of baseball's best all-around players last season. One of only seven major leaguers with a .300/.400/.500 offensive slash line, Rendon proved he can hit for average, hit for power and work the count. And he remains a wiz at third base, a Gold Glove Award finalist who would get way more attention if not for Nolan Arenado's nightly brilliance in Colorado.

Perhaps the most intriguing member of the Nationals lineup entering 2018 is the guy who has yet to play a full major league season but has shown more than enough so far to suggest he is capable of doing it all. Trea Turner had a bit of a ragged 2017, missing time both to a hamstring strain and then a fractured wrist. The latter injury came just as he was starting to peak, and he never was able to recapture it all before the season ended.

Still, Turner is well-positioned for a breakout season. It's still to be determined where he'll bat in Martinez's lineup, but his likely landing spot appears to be the No. 2 position, behind Adam Eaton and ahead of Bryce Harper, a place in the order that would leave anyone drooling. Turner's defensive work at shortstop, meanwhile, only figures to get better, which is saying something given how impressive he was last season.

Turner's injuries opened the door for Wilmer Difo to step into the starting shortstop's role for a long stretch last summer, and the young infielder seized the opportunity. Difo's .690 OPS may not have looked like much, but that number went up to a more respectable .732 when he started. And if nothing else, he turned plenty of heads in the field with his ability to both make the routine plays without incident and throw in some splashy gems as well.

Among the Nationals' savviest moves last summer was the trade deadline acquisition of Howie Kendrick from the Phillies. At the time, they needed the veteran to help hold down the left field job while Jayson Werth tried to come back from a foot injury. After re-signing him this winter, the Nats may need Kendrick's services more at second base than the outfield (depending on the status of Murphy's knee). Wherever he plays in the field, Kendrick will remain a consistent producer at the plate. A career .291 hitter, he raised his batting average to .315 last season, with a career-best .844 OPS.

Injuries to Turner and veteran backup Stephen Drew last year opened the door for Adrián Sanchez to make his long-awaited major league debut. The 27-year-old career minor leaguer more than held his own once he arrived in D.C., and he'll be back in 2018 as another one of the organization's reserve options in case of injuries.

The Nationals also will get a look this spring at prospects Jose Marmolejos (a first baseman and corner outfielder) and Kelvin Gutierrez (a third baseman who hasn't yet reached Double-A but was added to the 40-man roster this winter to protect him from the Rule 5 draft).