Not only are the Royals not sellers, they’ve actually made a prospect-for-veteran swap on deadline day. To help shore up their right field situation, they sent RHP Kyle Smith to the Astros in exchange for outfielder Justin Maxwell.
Maxwell is a solid role player, athletic enough to play all three outfield spots and with enough ability to provide some offensive value. In 763 big league plate appearances, he’s posted a .319 wOBA/97 wRC+, and UZR/DRS have liked his defensive contributions as well. Add it all up, and he’s racked up +3.8 WAR in just over a full season’s worth of playing time.
However, that’s a very defense-heavy number, and we’re dealing with 1,500 innings of outfield play from a 29-year-old. You have to regress his expected defensive contributions a good deal, which is why both ZIPS and Steamer forecast him to be roughly an average defender over the rest of the season. It doesn’t kill Maxwell’s value entirely, but he’s very unlikely to continue to produce at a +3 WAR per season pace.