After being traded from the Colorado Rockies to the St. Louis Cardinals this offseason, Nolan Arenado has joined his new team, and owners everywhere are wondering what a move away from Coors Field will do to his productivity. Paul Goldschmidt had his OPS drop by over 100 points when he moved from Arizona to Busch Stadium, but improved that number by 61 points to .883 in last year's shortened season. Where should Arenado and Goldschmidt be in your 2021 Fantasy baseball rankings?

Arenado hit at least 37 homers and drove in a minimum of 110 runs in his last five full seasons in Colorado, but a drop-off could spell disaster for those taking him with one of their early 2021 Fantasy baseball picks. Where does Arenado belong in your Fantasy baseball rankings 2021, and who are the 2021 Fantasy baseball sleepers you need to be aware of? Before you go on the clock, check out the 2021 Fantasy baseball cheat sheets and rankings from the proven computer model at SportsLine.

Last season, SportsLine's Projection Model identified several top Fantasy baseball sleepers, including Dodgers catcher Will Smith. The 25-year-old was No. 6 catcher in Fantasy baseball last year, outperforming Yasmani Grandal, Mitch Garver and Gary Sanches, who were all drafted well ahead of him on average. Smith wound up hitting eight home runs with 25 RBIs and posting a .980 OPS that was over 70 points better than in his breakout season in 2019.

The team at SportsLine was all over Smith as a Fantasy sleeper from the start. Their model had him listed much higher than expert consensus rankings, and anyone who listened to their advice was well positioned for a league title. 

Their model is powered by the same people who powered projections for all three major Fantasy sites. And that same group is sharing its 2021 Fantasy baseball rankings and cheat sheets over at SportsLine, helping you find Fantasy baseball sleepers, breakouts and busts long before your competition. Their cheat sheets, available for leagues on many major sites, are updated multiple times every day. Any time an injury occurs or there's a change on a depth chart, the team at SportsLine updates its Fantasy baseball cheat sheets.

In fact, when it came to ranking players in Fantasy football, SportsLine's Projection Model beat human experts last season when there were big differences in ranking. And the model was the closest to the hole overall, meaning it best pinpointed where every player would finish each week. That could literally be the difference between winning your league or going home empty-handed.

Now, the model has simulated the entire 2021 MLB schedule 10,000 times and revealed its top 2021 Fantasy baseball sleepers, breakouts, and busts. You can get its Fantasy baseball cheat sheets 2021 here.

Top 2021 Fantasy baseball sleepers

One of the 2021 Fantasy baseball sleepers the model is all over: Cubs center fielder Ian Happ. The former consensus top-100 prospect has had to battle for opportunities in a star-studded Cubs lineup over the last four years, but he has delivered consistently at the plate with a career .825 OPS and finally appears to be the everyday starter in center field.

Happ slashed.253/.361/.505 with 12 home runs and 28 RBIs in 2020. He also posted a career-high 91.1 mph average exit velocity and a career-high 48.5 percent hard-hit contact rate. The switch-hitter hit 11 of his 12 home runs from the left side of the plate against right-handed pitching and should be near the top of a talented Cubs lineup. That's why the model ranks him ahead of center fielders like Trent Grisham and Luis Robert, who are being drafted 13 rounds earlier on average.

Another sleeper that SportsLine's Fantasy baseball rankings 2021 are extremely high on: Orioles outfielder Trey Mancini. The 28-year-old finished third in AL Rookie of the Year voting in 2017 and then rebounded from a difficult sophomore season with 35 home runs and 97 RBIs while posting an .899 OPS in 2019. However, Mancini was unable to play in 2020 after receiving a cancer diagnosis.

Mancini went through treatment last year and arrived in Sarasota ready to begin his comeback. Mancini posted a career-high 90.3 mph average exit velocity and a career-high 9.3 percent walk rate in 2019 and says he's feeling better than ever. That's why the model ranks him as its No. 2 right fielder for 2021, ahead of players like Bryce Harper and Aaron Judge, who are going eight rounds earlier on average.

How to find proven 2021 Fantasy baseball rankings

SportsLine is also high on a first baseman with a Fantasy baseball ADP 2021 barely inside the top 10 who finishes ahead of studs like defending AL MVP Jose Abreu and Yankees first baseman Luke Voit. This pick could be the difference in winning your league or going home with nothing. You can see who it is here.

So which 2021 Fantasy baseball sleepers should you snatch in your draft? And which undervalued first baseman can help you win a championship? Visit SportsLine now to get Fantasy baseball rankings for every single position, all from the model that called Will Smith's huge breakout last season, and find out.