Trade deadlines have already passed in many fantasy leagues, so I'll focus more on lesser-owned players to assess their value, rather than potential buy-low or sell-high candidates. If your league doesn't cut off trading in August, remember that it's never too late to take advantage of a desperate owner trying to stay out of the basement.

Scouting players who may be undervalued and re-assessing players who may be overvalued is a weekly exercise that you should pursue. Fortunately, I have you covered. Here are a few players who are good buy or sell candidates based on their current performance compared to ownership levels. This could mean scooping them off waivers if possible or actively seeking a trade to acquire or discard certain players in order to maximize value.

I will include one player at each key position group (Infield, Outfield, Pitcher). Ownership levels are taken from Yahoo! Fantasy Sports.

• Fantasy baseball injury reports
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• Who should I start? Fantasy baseball player comparisons
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• Fantasy Baseball live scoreboard, daily leaderboards

Underrated Players - Week 23

Kolten Wong (2B, STL) 21% owned

In the second half, Wong is doing his best Tommy Pham impression. After bouncing back and forth from the minors, something the Cards have no problem doing with their young starting position players, Wong is making the most of his latest chance. In the last month, Wong has a .414 OBP, scored 19 runs and driven in 18. The limit to his game is a lack of help in the HR or SB departments, but he can be a perfectly serviceable middle infielder in leagues at least 12-deep.

Eddie Rosario (OF, MIN) 51% owned

It's September and Rosario is still hovering around the .300 mark (.293 as of Friday night) with 20 homers on the year. It wasn't clear if he would even lock down a starting job coming out of spring training, but he has done so with consistency that he hadn't shown in his first two seasons. He doesn't have the pedigree to far exceed his current power numbers, but the average is no fluke. He is better served as a third or fourth outfielder in mixed leagues, but one that you can feel fairly secure with.

Jack Flaherty (SP, STL) 28% owned

It's hard to call him underowned considering a quarter of all owners snatched him up before his first MLB start (which didn't go so great either). Still, Flaherty has been lighting it up all year in the minors to the tune of a a 2.18 ERA, 1.04 WHIP and a strikeout per inning. He'll get plenty of chances throughout September to show off his stuff, so he's worth a shot, even if you're in a non-keeper league.

Overrated Players - Week 23

Miguel Cabrera (1B, DET) 87% owned

It pains me to put him on this list, but the truth is a bitter pill to swallow sometimes. The fact that he's not 99% owned is telling enough - some owners are pulling the plug on Miggy to spare themselves the pain (I'm talking about his .230 batting average in the second half). It's too early to simply write him off for next year, as his struggles are purely injury-related. Then again, it's not encouraging to hear his manager proclaim that he will be likely deal with back pain until he retires. If you are in a shallow enough league and have better options on the waiver wire, you won't be blamed for performing a mercy-kill.

Matt Kemp (OF, ATL) 82% owned

Like Cabrera, we can blame injuries for a lot of Kemp's fall-off in the last couple of months. Unfortunately, he hasn't picked up the slack since returning from the DL on August 19. Sure, he's still batting .291 on the year and has maintained his average fairly well, but that's not what we need from him. Kemp has only gone deep three times in the second half and has all of five homers since June arrived. It's a bit frustrating to own him at this point because it's too late to trade him, but he isn't playing bad enough to be dropped either. He's simply performing as a low-end OF3 that looks like an older version of the aforementioned Eddie Rosario.

Greg Holland (RP, COL) 87% owned

I'm also not going to say that Holland needs to be dropped or even benched (yet), but get one finger ready on the trigger. Although he's thrown less than 50 innings this season, having taken the year off in 2016 recovering from TJS may be catching up with him. Holland was placed on notice by manager Bud Black after two straight disastrous blown saves last week. In the last four weeks, he's allowed twice as many earned runs as he's pitched innings and has only locked down two saves. The last thing you want is a suddenly reliable closer blowing up your ERA in the final weeks of the season. Keep a close eye on this situation - the Rockies won't mess around with their wild card position in order to assuage Holland and his confidence.

More Risers and Fallers

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