How worried should you be?

Every fan hates their team's medical staff. It's canon. A big part of the reason is because the team has no real impetus to release accurate information. Teams want to maintain an negotiating advantage in any trade talk or free agent signing they may be interested in and the best way to do that is to downplay your actual need of a player. You can't flat-out lie, but you can toss out a standard best-case recovery scenario and hope that helps. The downside of that is fans end up buying it and then thinking the team has no idea what they are doing when the guy ends up missing more time than they said. But that's not much of a downside - fans still buy tickets.

Everytime a player gets injured fans shouldn't rely on Nats reports only. Instead they should read every interview, take in every piece of data, to figure out exactly how they should modify what the team says to get the most accurate picture.

All that being said let's look at the Nats current injuries and see where they may more realistically stand.

Adam Eaton - recovering from a torn ACL. 
Team says - On Track for Opening Day
Seen - Had surgery May 10th. Initial prognosis was 6-9 months, was slightly ahead of schedule as he began weight-bearing exercises about a week early (remember the "maybe he could play in the playoffs!" talk?). Now seems perhaps slightly behind. He said he'd be ready for Spring Training, but in December Martinez was already saying Opening Day was goal, not Spring Training.

He's not participating in everything or at full speed and hasn't appeared in a game yet. He is participating in almost everything and at what he says is 70% speed.
What adjustment - I think we can still buy into an Opening Day start now. Since Adam hasn't played in almost a year you probably want more than a handful of games in his pocket before the season starts but that just puts the "worry line" at say... March 19th. 
What you want to see - As soon as he plays a game it's good. Until then you'd like to see some sort of ramping up and at least one "any day now" kind of message about when we'll see him play.

Daniel Murphy - recovering from knee surgery
Team Says - On Track for Opening Day
Seen - Had surgery October 10th. Even though team said Opening Day, timetables were never set because they didn't want to cause "unnecessary alarm" if he didn't hit them. Usual time tables for this are 6-12 months, which would put Murphy back in the lineup anywhere from late April or 2019.

He's fielding some grounders while on a knee. He's running, though at least initially not with all his weight (think this). He's playing catch. 
What adjustment - Opening Day was an optimistic forecast to start with. Given what we've seen here it seems even more unlikely.  Stick with the usual timetables for now and figure late April as a return date and adjust accordingly - probably later - as we get more info
What you want to see - Just a progression. I think you'd want him doing real baseball activities, taking batting practice, fielding balls while, you know, standing up, sometime before the end of Spring. Once he can do those things, then you can worry about doing it at full speed and then it's about rounding yourself into shape. If we're taking Eaton as a guide that's probably a month or so buildup. 

Koda Glover - recovering from shoulder issues
Team Says - No surgery. Shut down in September with plans to be ready for next year. Initially no one said they saw any issues as he was cleared to begin throwing again in November. Unclear if he started throwing off a mound in January as planned.
Seen - Didn't take the mound when he got to Florida. We were told he showed up with shoulder issues. MRI confirmed inflammation. Shut down. 
What adjustment - Pretty much put Glover out until you hear otherwise. We can't set up a timeline until he starts throwing again and we see where they are starting him from. If they are starting with the idea he's getting on the mound soon (which doesn't seem likely) he could be ready a month or so after that. If he's starting over from soft tossing it could be 3 months. Personally I'll put my money on Summer 2018. 
What you want to see - On the mound sometime during Spring.

Joe Ross - recovering from Tommy John
Team Says - Had surgery mid July. Team only said sometime 2018. As Spring opened Ross said he was aiming for August.
Seen - Ross is throwing 75 feet. No one said if this was ahead, on, or behind schedule.
What adjustment - None. Ross' stated goal is a reasonable good case and too far out to judge currently.
What you want to see - Probably just 90 feet before Spring is out. I think that would be enough. We're still far out here so there's a lot of leeway.

Matt Adams - foot blister
Team Says - Couple of days
Seen - Nothing
What adjustment - Nothing
What you want to see - Him playing by Saturday

Bryce Harper - ingrown toenail
Team Says - Could of days, maybe
Seen - Nothing
What adjustment - None
What you want to see - Him playing before Monday