This article is part of our The Long Game series.
With the season having reached the quarter pole, overall trends and player performances are taking shape. Homers remain way, way up, while strikeouts continue to rise. More pertinent to keepers and dynasty leagues, the flood of top prospects getting called up continued this week with Brendan Rodgers and Austin Riley, the latest names in a parade that stretches back to Opening Day assignments for the likes of Eloy Jimenez and Chris Paddack.
Farm systems aren't the only way to acquire talent that can form the core of future championship rosters, though. Plenty of less heralded players who came cheap this spring in drafts and auctions have exploded out of the gate in 2019, and determining which of them should be traded before they lose value, and which could be a key piece of your foundation moving forward, is a key skill. Whit Merrifield is the best recent example of how critical these decisions can be. Keeper-league GMs who picked him up for a song at the 2017 auction table either held onto him and have reaped the benefits ever since, or "sold high" that summer expecting him to fade and have likely regretted it ever since.
Here's a list of some of the biggest surprises through mid-May – five hitters and four pitchers – and a look at whether they're likely to keep it up and are worth protecting and building around, or whether you'd be better off cashing in now.
Josh Bell, Pirates: During the