You're probably tired of being told not to overreact to the first week of the MLB season by Fantasy analysts, but I don't want to be misunderstood here: "Don't overreact" doesn't mean "don't react." We've only got four day's worth of games -- not even a full turn through the rotation -- but these games still count. 

And, as much as we can tell you not to overreact, you've got waiver-wire claims to make and lineup decisions to sort through, and you can't just sit idly by while the rest of your league makes moves. We're covering our top waiver-wire targets every day on CBS Fantasy and the Fantasy Baseball Today podcast, but on Monday's episode we also talked about some early season overreactions, and whether they are actually overreactions. You can listen to the episode below to catch up on everything you need to know from the first weekend of the season:

And now, let's play a little "Believe it or not" with some of the biggest storylines and performances from this weekend's games, starting with Shohei Ohtani's impressive debut:

Shohei Ohtani is a must-start pitcher and hitter!

Don't believe it. He was incredibly entertaining to watch Sunday, giving us a glimpse of just how overwhelmingly dominant he can be: 

Of course, he also walked five in 4.2 innings, so it's not like he was perfect. As a hitter, I actually do think Ohtani is a must-start option, especially if he'll be batting in games where he pitches -- he hasn't missed a game yet as a hitter. The pitching side is where I'm a bit more skeptical. I think the upside is higher there, to be clear -- Ohtani could be a top-10 pitcher on a per-inning basis -- but there's still some rust here. And, given that he's likely to be a two-start pitcher very rarely because he's in a six-man rotation, I would probably prefer to use him as a hitter right now. Of course, he could very well get there before long. The skills are there on both sides. 

Ketel Marte is an elite hitter!

Believe it. You should've been listening to me back in spring! I've been touting Marte's virtues for months now, and he hasn't disappointed so far. Maybe it's just confirmation bias at play, but Marte's hot start looks a lot like his last few seasons, at least with the underlying numbers -- he has a 42.9% hard hit rate, and his 89.2 mph average exit velocity is right in line with 2019 and 2020 as well. He didn't hit for much power in 2020, of course, but I was expecting a big bounce-back more in line with 2019, so that doesn't bother me much -- he was dealing with a wrist injury last season and has already matched his homer total. His elite bat-to-ball skills and underrated power make Marte a hot start to buy into.   

Luis Castillo is a bust! 

Don't believe it. Velocity isn't one of those stats that you can fluke your way into. You can go 8 for 8 and still be a bad hitter, but if you throw 99 mph it's because … you can throw 99 mph. Of course, just because velocity is a direct measure of something a player is doing doesn't mean it can't fluctuate from start to start. It does for every player. Castillo's velocity was down a pretty alarming amount in his first start, and if he's averaging 94.9 mph with his fastball -- he was at 97.4 last season -- in May, I'll be very concerned. For now, I'll just chalk it up to Castillo pitching in unseasonably cold temperatures. 

Buster Posey is back!

Believe it. It's all relative, of course; Posey isn't likely to be back to the MVP form of his peak, obviously. But I think we'll get a better version of Posey than we've seen since at least 2018, if not earlier. He was clearly not healthy in 2019, as he hit .257/.320/.368 with just seven home runs in 114 games before undergoing offseason hip surgery. That procedure plus the year off in 2020 were probably very good for Posey, who surely comes into the season fresher than he's been in years. Posey's opening day homer off Marco Gonzales came off the bat at 106.5 mph, a range he only reached once after April in 2019. Posey has never lost the elite bat-to-ball skills, and if this start is any indication, he's going to be a must-start catcher for as long as his body can hold up. 

Julian Merryweather is the Blue Jays closer!

Don't believe it. Merryweather has the first two saves of the season for the Blue Jays, and he's looked pretty incredible in doing so, striking out five of the first six batters he's faced. However, there are extenuating circumstances that led to those saves. In the opener, Jordan Romano pitched a scoreless bottom of the ninth in a tie game, a pretty traditional closer usage. And Sunday, Romano came in to pitch the bottom of the eighth with the 1-2-3 spots in the Yankees order up. It's possible Merryweather is the closer now, but I want to see a more typical situation come up before I call it. If the Blue Jays turn to Romano with a three-run lead in the eighth inning Monday, then I'll believe it's Merryweather's job. 

Jose Berrios is a top-12 SP!

Don't believe it. I mean … he might be! I had him ranked 17th coming into the season in a points league, so he wouldn't need to leap far. And, another leap in fastball velocity -- from 93.4 mph in 2019 to 94.5 in 2020 to 95.3 Saturday -- would be a pretty good reason to think he's made that leap. But, I'll need to see more from Berrios before I buy that. His issue has never been that he can't pitch like an ace from time to time -- the issue has been consistency. Let's see how the next two to three starts go before we change our view of him. 

Yermin Mercedes is a must-add!

Don't believe it. With a caveat -- in leagues where he is catcher eligible, Mercedes is definitely a must-add. However, right now, he's just utility-only in CBS Fantasy leagues, and let's not forget how we were discounting guys like Jorge Soler and Franmil Reyes for being utility/DH-only in drafts. As good as he's been early on -- good enough to seemingly lock himself in as the DH at least for the time being -- Mercedes has a max exit velocity of 104.6 mph -- a sign that he may not have prodigious raw power to draw from. Mercedes could be a useful Fantasy option, but it's pretty unlikely he'll be better than Soler or Reyes, so don't break the bank for Mercedes, and don't drop someone you believe in for him. 

Nick Castellanos is having his breakout season

Believe it. Another situation where there may be some confirmation bias at play, but Castellanos had four batted balls hit over 100 mph Sunday, giving him five in three games. Castellanos hit the ball with authority in 2020 and had a career-high .261 ISO, but had a .257 BABIP, compared to his .330 mark. Maybe it's confirmation bias, but Castellanos was such an obvious bounce-back candidate that all I needed to see this weekend was that the skills are still there. 

Nate Lowe is a must-add player!

Don't believe it. But that's not to say Lowe is not worth adding. He definitely is. He's always been a talented player, and he's getting the chance to play everyday for the Rangers early on. That's a good sign -- especially since they got him in the lineup at DH Sunday. However, his issues in Tampa weren't just because he didn't get regular enough playing time -- he also really struggled to make contact, with a 32.2% strikeout rate for his career. Lowe is off to a great start, and if you've got a spot for him on your roster, it's well worth taking a chance on. But he'll need to keep producing this way for at least a few weeks before he starts moving up my first-base rankings. 

John Means breakout season is happening!

Don't believe it. The hype that built around Means this offseason was at least in part tied to the increased velocity on his fastball in 2020, so it's hard to square his dominant first outing against the Red Sox with the fact that his velocity was down two full ticks from last season. However, Means has apparently been dialing back his velocity a bit since early in the spring, hoping to maximize his command and get the most out of his repertoire. That's a reasonable enough explanation for why the velocity is down, but when we saw him pitching in this range in 2019, he had a 4.05 xERA, 4.41 FIP< and 5.41 xFIP, and wasn't exactly a must-start Fantasy pitcher even with a 3.60 ERA. I think Means is an interesting option, but I'm not exactly beating the door down to add him this weekend. I'll need to see a lot more than this.