Baseball is back, baby! The Seattle Mariners and the Oakland A's open against each other today in Tokyo, signaling the long-awaited — but earlier than ever — return of MLB.

The year ahead is full of questions, though. It's undeniable at this point that baseball is changing: The contracts are bigger, the rule-change rumors louder, and the balls juicier than ever before. Ahead of the 2019 season, here are the biggest and most exciting storylines that will be worth following for the next seven months.

Is the opener here to stay?

There is some debate over if the "opener" is really the next big thing in baseball. While the Tampa Bay Rays were the most enthusiastic team to try having a relief pitcher start the game, franchises as varied as the Oakland A's, Texas Rangers, and even the Los Angeles Dodgers attempted the newfangled strategy last year. As ESPN's David Schoenfield remarked at the end of last season, "It's remarkable that a sport as old as baseball can still find ways to innovate." The question will be if it has staying power as critics have slammed the strategy for "not working."

Who is the ace on the Dodgers?

If you'd asked this at any point in the past six years, it'd have been a no-brainer: Clayton Kershaw, one of the greatest pitchers to have ever lived, has brought pride to L.A. — if not quite a World Series trophy. Now, though, Kershaw is staring down 31 (happy belated birthday!), with the Steamer projections system predicting his ERA will creep up to 3.23 this year. He's got competition for his spot as the team's ace, too: Walker Buehler made a case for himself as the best pitcher on the team in 2018, boasting an ERA of 2.76 with 148 strikeouts, while Hyun-Jin Ryu, whose ERA dipped under 2.00 last year, has also impressed in southern California. Any way you look at it, it's a scary rotation, and an exciting one when anyone could come out ahead in 2019.

Can Trevor Bauer get the Cy Young?

Indians ace Trevor Bauer wants a Cy Young. Actually, to be more specific, he wanted last year's Cy Young. The famously trollish pitcher sees no reason to be polite about it — "plot twist, I was better than [Indians' pitcher Corey] Kluber this year" he even tweeted of his teammate, who came in third in the voting. But Bauer isn't all bark; as a great Sports Illustrated profile of the pitcher reveals, Bauer is trying to improve his game with methods as varied as stimulating his brain with electricity to obsessing over things like RPM and spin rate. Will it pay off? Bauer thinks so: "My new five-year goal is to be the most internationally recognizable baseball brand," he told SI. We'll see where this year puts him on that path.

Is Vladimir Guerrero Jr. worth the hype?

Vladimir Guerrero Jr. has spent practically his whole young life being the next big thing; he signed with the Toronto Blue Jays for $3.9 million when he was just 16. Having just turned 20, the infielder and son of hall-of-famer Vladimir Guerrero Sr. is the top prospect in all of baseball and, despite never appearing in a single Major League Baseball game, already looks to be a lock for AL Rookie of the Year. He's projected to bat over .300 this season, but will be starting in the minors due at least in some part to Toronto gaming the system to keep him under team control for longer. He's proven he's good, but what remains to be seen is if, when Guerrero Jr. finally gets to join the team, he'll be able to meet the monumental expectations that lay ahead.

Is this the beginning of the Phillies' reign?

You don't write a player a 13-year, $330 million dollar contract if you just want to contend in an October or two. With the acquisition of Bryce Harper, the Philadelphia Phillies signaled they aren't just looking to make the playoffs this year — they're here to stay. With the addition of Andrew McCutchen, and with Aaron Nola and Jake Arrieta in the rotation, it's certainly a formidable team. That being said, it won't be easy becoming king; the NL East is a competitive division this year, with the New York Mets and Washington Nationals both poised to put up a fight. As The Ringer observes, "Almost all of the notable departures from NL East teams — Harper, Realmuto, Ramos, Sánchez, Suzuki, Jorge Alfaro — went to other NL East teams, preventing the division from leaking talent."

Will this be the last year of baseball as we know it?

Earlier this month, MLB and the Atlantic League announced major changes to gameplay, including computer assisted strike zones; a requirement for pitchers to face a minimum of three batters, or reach the end of the inning, before being swapped out; and two infielders on each side of second base, among other changes. This much is now certain: It is only a matter of time before the Major Leagues begin adopting similar tweaks to the game. Already this off-season it was rumored that the DH could be axed as early as Opening Day. While there haven't been any major structural changes of that sort just yet, this will in all likelihood be the last year of baseball exactly as we know it, and it will be fascinating to hear how players weigh in on the rumored adjustments over the course of the season.