Invest, or not: Youngsters with upside

The past couple weeks, I've been focusing on prospects, posting my Top 50 on March 2 and Nos. 51-100 on Tuesday. But what about the talented young players who aren't rookies but have yet to truly establish themselves as viable fantasy options?

Is Justin Smoak destined to be a fantasy bust? What about Brett Wallace? How good is Peter Bourjos? Kila Ka'aihue?