A must-follow story in this spring training is Aaron Barrett’s comeback attempt with the Washington Nationals. Sidelined much of the last three years by a couple of major arm injuries, the ex-Ole Miss standout threw a bullpen session in the Nats’ Florida camp this week. “(T)his was a good first step,” the 31-year-old right-hander told nbcsports.com while acknowledging he still faces a long road back to The Show. Barrett was a ninth-round pick by Washington out of UM in 2010, quickly established himself as a prospect and made the big leagues in 2014. In 90 games over two seasons with the Nationals, he posted a 3.47 ERA. But an elbow injury that required Tommy John surgery and then a horrific fractured arm injury cost him the 2016 and ’17 seasons and almost ended his career. Re-signed by Washington, he finally made it back to the mound in a pro game last summer and wound up with a 1.74 ERA in 20 appearances at the short-season Class A level. Re-signed again, Barrett got a non-roster invitation to big league camp, where he has a lot of folks rooting for him. … Mississippi State product Nate Lowe is not on Tampa Bay’s 40-man roster but will be in spring camp getting a long look as the first baseman of the not-too-distant future. Lowe mashed 27 homers, drove in 102 runs and batted .330 over three minor league levels in 2018. Yes, he was the organization’s minor league player of the year — in a loaded farm system — and is now its No. 13 prospect. The 6-foot-4, 235-pound, lefty-swinging first baseman, 23, is starting just his fourth pro season, and the Rays may not want to rush his MLB arrival. Yandy Diaz and Ji-Man Choi are the first-base candidates on the club’s current roster. Should they falter, Lowe stands ready. … Kansas City craves speed, something Billy Hamilton has in abundance. The Royals signed the former Taylorsville High star as a free agent and will deploy him in Kauffman Stadium’s spacious center field. “If you play in our ballpark,” Royals GM Dayton Moore said in an mlb.com piece, “you have to be able to defend. Billy Hamilton will give us that.” Hamilton’s bat, found wanting in Cincinnati, needs to perk up if his speed is to be impactful on the bases. After averaging almost 60 bags a season over four years, Hamilton’s total fell to 34 last season. It wasn’t because he has slowed down or that the Reds were holding him back. “You got to get on base to run,” Hamilton told mlb.com. “It’s not their fault. It’s all on me.” He hit .236 in 2018 with a .299 on-base percentage. He has a .298 career OBP.