Aaron Barrett, right, has been impressive this spring.  (AP Photo/David Goldman)

The Nationals have their first of two scheduled off days of the spring today, which happens to come after yesterday’s rainout in Lakeland. Tanner Roark, yesterday’s scheduled starter, will pitch in a minor league game at 1 p.m. With no other baseball action to watch and report, why not run through a few observations, notes and assorted thoughts?

 The Nationals have an open mind about the final spot on their bench, with names like Jeff Kobernus and Zach Walters still being discussed. But the final opening-day roster spot will almost certainly come down to either utility infielder Jamey Carroll or first baseman/outfielder Tyler Moore.

Moore provides more power off the bench and more offensive upside. Carroll has experience, a .331 average as a pinch hitter and a reputation for dependability. One factor to consider: Carroll, 40, has accomplished all he could have hoped for in baseball and may decide to call it a career if he doesn’t make the 25-man roster. Moore has a minor league option left. If the Nationals keep Carroll and decide they need Moore, they would have that choice. The opposite may not be true.

● Aaron Barrett seemed like a long shot to crack the opening day roster at the start of camp, more of a relief prospect to keep an eye on for the future. But now it looks like he has a real shot at the final bullpen spot. Ryan Mattheus has been hurt. Christian Garcia hasn’t quite recaptured his velocity. Luis Ayala has been sharp at times, but he also allowed four runs in one outing and five in another.

Barrett, meanwhile, has yet to allow a run. Barrett, who was Harrisburg’s closer last year, throws a nasty slider and spots his fastballs in the low-to-mid 90s. Matt Williams kept open the possibility of taking a lefty for the last spot even with Ross Detwiler now in the bullpen, so Xavier Cedeno and Michael Gonzalez shouldn’t be counted out. But so far, Barrett has been the best of a crowded field.

● What look like tough decisions now may seem easier in a week or so, in the days before the Nationals head north. “They cut themselves,” one Nationals official said.

● At last check, there’s nothing doing with contract negotiations between Jordan Zimmermann and the Nationals.

● After the news of Ross Detwiler’s move to the bullpen came out yesterday, two scouts texted me wondering if he was available in a trade. The sense is, though, that the Nationals didn’t move Detwiler to the bullpen because they view him as expendable. They think he’ll be dominant and provide something with his power that other relief options couldn’t.

● Blake Treinen is not on the 40-man roster, but he’s still in camp. The right-hander, acquired with Ian Krol and A.J. Cole in the trade that sent Michael Morse to Seattle, been turning a lot of heads. One of his fastballs in a game last week zipped at 98 mph. One scout said he clocked Treinen’s fastball at 101 during an amped-up start in one of Harrisburg’s playoff games last year. It wouldn’t be a surprise at all if he finds himself in Washington at some point this summer.

● Danny Espinosa’s numbers (6 for 29) don’t show it, but the Nationals have been pleased with the changes he’s made to his approach with two strikes. Pitches that last season he would have taken a full swing at and missed, like a slider down and in, he’s now taking a more controlled swing at. He’s been fouling off or putting into play more of those tough pitches. He has five strikeouts and two walks. The Nationals are operating as if he’ll make the team.