You can start, if you want to, just for fun, with some of the things Mookie Betts is not, right before you get to all the pretty wonderful things he is on a baseball field. Betts is not Mike Trout, for example. He's not ever going to make the kind of money Bryce Harper is going to make after this season. Betts has not been past the first round of the playoffs yet in his Red Sox career. He's not an American League MVP Award winner, at least not yet, even if he did finish second in the voting once.
You want one more? Betts is not included nearly often enough in the conversation about the best young players in the deepest and best crop of young players in all of baseball history. But now we're talking. Because when you add it all up with Betts, when you look at his offense and at his defense, you need to ask yourself a question:
How many two-way players are better than the leadoff man for the Red Sox who, oh by the way, has been the best player in baseball this April?
Here is what Orioles manager Buck Showalter, who has seen plenty of Betts in the AL East, says about him:
"I've told anyone who will listen. He's the best right fielder I've ever seen in person. The dynamic he creates for them defensively in right field at Fenway is a big advantage for Boston. Special player. Game changer. The term five-tool player is used loosely. But it aptly describes him. One of my most favorite players in our game."
Here is what AJ Hinch, whose Astros beat Betts' Red Sox in the AL Division Series last season, says about Betts:
"He is an incredible talent. I love his energy, and impact. Offensively, he is never off the fastball, and can time up any velocity. A dangerous hitter because of how he barrels up pitches. Defensively, he has every skill you look for. He's a premier player in this league. He can do it all on any given day."
Again: We talk a lot, and properly so, about Trout and Jose Altuve and Aaron Judge, about Harper and Manny Machado and Hinch's gifted shortstop, Carlos Correa -- another wonderful two-way player, at bat and in the field. But we do not talk nearly enough about Betts, except perhaps right now, when he is hitting .391 and hit three home runs the other night and might have had a chance for four if there hadn't been a double play before his last at-bat.
Betts has now hit three homers in a game three times already in his five-year career. It happens to be something that Willie Mays also did three times, and Joe DiMaggio did three times. Babe Ruth did it twice. So did Ken Griffey Jr.

These are Betts' stats for his four full seasons in the big leagues, starting in 2015 (he played 52 games in '14, hit .291, with five home runs and 18 RBIs), all the way through Thursday night's game against the Angels:
2015: .291 AVG, 18 homers, 77 RBIs, 92 runs, 21 stolen bases, .820 OPS.
2016: .318 AVG, 31 homers, 113 RBIs, 122 runs, 26 stolen bases, .897 OPS.
2017: .264 AVG, 24 homers, 102 RBIs, 101 runs, 26 steals, .803 OPS.
2018: .391 AVG, 6 homers, 14 RBIs, 22 runs, 1.277 OPS.
In addition to his six homers, Betts has scored 22 runs -- the most through 18 games in Red Sox history. And then there is his play in right field, which is as good as you will ever see with your own eyes, just as Showalter, who has seen plenty in his baseball life, said.
Of course with a player's defense, we now have better tools than ever to measure performance, and Betts is clearly the No. 1 right fielder in this area. According to Statcast™'s Outs Above Average (OAA) metric, Betts has 36 OAA since the start of 2016, which is 10 more than anyone at that position. That's right, even better than Jason Heyward, who is second to Betts with 26 OAA in that time, and was pretty much given $184 million because he is a terrific fielder himself.

Since the start of 2015, Betts has a WAR of 23.4 (per Baseball Reference), behind only Trout at 28.1. He is a force of baseball nature. Betts has come into 2018 swinging, being more aggressive than ever at the urging of new Red Sox manager Alex Cora. He is, in Hinch's words, "barreling up" on just about everything he sees, as the Red Sox have barreled to the top of the standings for all of baseball so far. Betts does not hit home runs the way Harper does, or Judge does. But among the sport's biggest stars in the outfielder, only Trout is in the same conversation with him. 
"There's a different approach [this season]," Cora said of Betts on WEEI radio on Thursday. "I think [Betts] set the tempo on the first-pitch fastball of the season when he almost took it out of the ballpark in Tampa against [Chris] Archer. Instead of just working the count, taking pitches right down the middle and falling behind, he's ready to attack from the get-go. You can see now pitchers, they know what's going on so they have to grind from the first pitch with every at-bat. I don't think it's a hot stretch. I think this is the guy. Obviously his OPS is not going to be 1.400. He'll be over .900, and that's a good leadoff hitter. I mean, that's elite. That's what we wanted from the get-go, and he's done an outstanding job."

Yeah. Betts has done that, before the age of 26. He is that good, well on his way to being one of the great players of his time. Silly to talk about what Betts is not for even five more minutes. Only what he is. Right there in front of everybody's eyes.