Each week, FantasyPros publishes a fantasy baseball trade chart. The chart contains player values designed to help you assess the overall weight of both sides of a trade.

The weekly trade charts also keep track of the changes in a player’s value from the previous week. But sometimes, the reasons for a change aren’t obvious. “Why is player X gaining three points in value this week when player Y, who had an even better week, remained the same?”

Good question, reader. There are many answers as to why any given player moves in value from one week to the next. And in this article, we’ll examine some of the biggest risers and fallers each week, and explain the movement.

Here are some of the most notable risers and fallers in the FantasyPros Week 5 Trade Value Chart:

Risers

Michael Kopech (SP – CWS). Week 5 Value: 10. Previous Value: 4. Change: +6

It’s the second straight week a White Sox starter is making a major move up the trade chart, and there’s an argument that Kopech should be higher. He leads the league in ERA (0.93) and has a 0.97 WHIP. His fastball, which he throws 66.1% of the time, has been dominant, with a .138 BA, .185 SLG, and .210 wOBA. And the pitch ranks in the 96th percentile in spin rate.

But there are plenty of reasons why Kopech’s value, though rising, should remain in check. Because of injuries and him opting out of the 2020 season, Kopech has thrown just 69 1/3 innings combined over the last three seasons. So even in his best-case scenario, he’s not going to be out there pushing 180 innings.

His walk rate is 11.4%, fifth-worst among qualified starters. He has yet to allow a home run despite having the second-highest fly ball rate among qualified starters (52.9%) and pitching in a hitter-friendly home park.

In other words, it all looks good now, and for the most part, it is. But it’s not at the elite starter level just yet, and there are plenty of reasons to think that Kopech won’t quite get there this year.

Nestor Cortes (SP – NYY). Week 5 Value: 10. Previous Value: 5. Change: +5

Yeah, I don’t really get it either. But some things just are the way they are, and Nestor Cortes is really, really good right now.

His fastball averages just over 90 miles per hour and yet he has allowed just a .206 BA, .235 SLG, and .260 wOBA against the pitch. Andrew McCutchen explained the pitch’s effectiveness after Cortes dominated again on Monday:

Nestor Cortes’ fastball plays up. Meaning his 91-94 actually feels like 97. Mix that with him messing with a hitters timing, throwing from diff arm angles, and locating well, he can be very difficult to hit. He showed that today

– Andrew McCutchen (@TheCUTCH22) May 9, 2022

Cortes’s cutter is equally as effective, and his results have been excellent. A 1.41 ERA, a 0.97 WHIP, and a 33.9% strikeout rate. The ride may end, and Cortes shouldn’t be valued as an elite starter just yet. But fantasy managers should not shy away from trading for him.

Fallers

Jose Berrios (SP – TOR). Week 5 Value: 14. Previous Value: 19. Change: -5

Take the name off Berrios’ jersey and he’s a drop candidate. His 5.34 ERA (backed up by a .7.71 xERA, mind you) and 1.64 WHIP are hard to look at. His 14.8% K-rate is a career-worst by a mile. He ranks in the bottom three percent of MLB in xBA, xSLG, xWOBA, and xERA.

In other words, Berrios isn’t missing any bats and he’s getting hit hard consistently. He also plays in an extremely hitter-friendly venue in a division full of tough lineups.

Berrios has one thing going for him and that is his track record. He’s been one of the steadiest pitchers in the game for the past five seasons. And his lengthy run of success earns him a little rope.

But if you’re looking for anything to grab onto in terms of his performance this year, it’s just not there. So downgrading him in trade value is an obvious and necessary move.

Salvador Perez (C – KC). Week 5 Value: 23. Previous Value: 28. Change: -5

Perez has two things going for him. He plays catcher and he hits the ball hard. So, he’s going to rank high in the trade chart absent injury unless he falls off a cliff entirely.

But, yeah, things don’t look great right now. His strikeout rate is a career-worst 27.8%. His batting average, slugging percentage, and expected statistics are noticeably down, even for a typical catcher.

And yet his five home runs lead the position. His 10 RBI rank fifth. His 10 runs rank ninth.

On his worst day, Perez is still probably the best catcher in fantasy baseball. But he’s not quite in an entirely different stratosphere than every other player at the position at the moment.

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Dan Harris is a featured writer for FantasyPros. For more from Dan, check out his archive or follow him on Twitter @danharris80.