It's Kentucky Derby weekend, but, in MLB, teams are always jockeying for position. So it will be this weekend, which features some important division duels, a big league border crossing and a matchup of two of the best clubs the American League and National League have to offer. Here are five key storylines as the weekend post time nears:
1. From Ichiro to Ohtani (plus Pujols' 3,000 chase)
The Mariners went hard after Shohei Ohtani this offseason, selling him the legacy Ichiro Suzuki established when he made the move from Japan to the big leagues in 2001 and launched a Cooperstown-worthy career. Ultimately, Ohtani went elsewhere in the AL West, and, ironically, the Mariners wound up signing Ichiro himself this year when injuries invaded their outfield during Spring Training.
Now, Ohtani makes his first trip to Seattle this weekend, just as Ichiro has left the playing field and joined the front office as the Mariners' special assistant to the chairman. Every Angels game right now is an opportunity to witness history, because Jose Pujols is sitting on 2,999 hits. But Ohtani is expected to start Sunday's 4:10 p.m. ET game at Safeco Field (that is not yet confirmed as of this writing) in a sort of passing of the torch from one Japanese superstar to another.
It would have been quite a moment of international intrigue if Ohtani had faced Ichiro, but squaring off opposite Felix Hernandez in Ohtani's first start since April 24 (because of an ankle issue) ain't so shabby, either.
Beyond all that, the Angels and Mariners have shown early signs that they could keep the defending-champion Astros honest out West, so this is a compelling series, in general.
2. Spring Classic?
Speaking of the Astros, they've got their hands full this weekend. Is it too soon to call their three-game series against the D-backs a potential World Series preview? Nah, it's never too soon!
Arizona, which just got finished with a series against the reigning NL pennant winners, has been simply awesome this season, and its start is especially remarkable considering the club has done it without Steven Souza Jr. and Jake Lamb in the lineup. Though Souza was activated off the DL on Thursday, Arizona's rotation has been battered more recently, with Taijuan Walker's Tommy John surgery and Robbie Ray's oblique strain. Enter Kris Medlen, who will make his first Major League appearance since 2016 when he starts tonight's 9:40 p.m. ET series opener opposite Gerrit Cole at Chase Field.
This will also be AJ Hinch's return to the place where he got his first managerial opportunity -- a job that didn't go nearly as well as his time in Houston has.
3. Oh, Mexico
There will be Cinco de Mayo celebrations aplenty this weekend, and south of the border down Mexico way -- well, specifically, Estadio de Beisbol in Monterrey -- they'll have baseball on hand for the holiday. The Padres and Dodgers will play a three-game set that is a chance for MLB to tap into the Mexican market and, for that matter, a chance for Padres third baseman and Guadalajara native Christian Villanueva to get the love he deserves.

Villanueva (the lone Mexico native on either roster) is in the midst of one of the hottest starts in the Majors. He won NL Rookie of the Month on the heels of a March/April in which he slashed .321/.411/.692 with eight homers -- the second-most before May 1 in franchise history (interestingly, the most were the nine hit by fellow Mexico native Adrian Gonzalez in April 2009).
• Villanueva's dreams come true in Mexico return
So there are sure to be sweet serenades for Villanueva in his homeland, and there will be other things worth celebrating in this series, including the legendary Fernando Valenzuela, who will throw out the ceremonial first pitch before tonight's 9:10 p.m. ET opener (live on MLB Network). Mexican fans are passionate about baseball, and this series will more deeply align them with their neighbors to the north.
4. NL Central of attention
The NL Central is baseball's deepest division at the moment, with the Brewers, Cardinals, Cubs and Pirates all holding winning percentages of .531 or higher. The combined 15-3 record against the last-place Reds doesn't hurt.
Just two games separate the first-place Brewers from the fourth-place Pirates, who make their first visit to Miller Park this weekend. Tonight's 8:10 p.m. ET opener features Nick Kingham opposite Junior Guerra for Kingham's second big league start. How did his first go? Well, he only became the second pitcher since at least 1908 (joining Johnny Cueto) to allow one or fewer hits, strike out nine batters and not walk any in his MLB debut.

This will be the second time this season that the Cubs and Cardinals square off, and their first series at Busch Stadium. Both of these clubs have gotten off to solid starts despite erratic offenses. Anthony Rizzo (.549) and Marcell Ozuna (.591) surprisingly rank among the lowest-qualified OPS marks in the NL in the early going. Maybe this will be their time to shine.
5. Rematch … and preview?
The Yankees and Indians staged quite an AL Division Series against each other last October, when New York stormed back from an 0-2 hole in the best-of-five (after an epic Game 2) to punch its ticket to an ALCS appearance that few expected going into the year.
These days, big things are expected for both of these ballclubs, so their reunion in the Bronx this weekend, beginning with tonight's 7:05 p.m. ET game, feels like a potential October preview. The Yankees are coming off an entertaining four-game set against an Astros team that is also likely October-bound, so this week is an interesting early litmus test for them.
Josh Tomlin has stepped up for the Tribe in recent postseasons, but he's pitching for his rotation life these days with the 9.16 ERA he'll take into Friday's start opposite long-ago Indians ace Carsten Sabathia. Both of those guys are survivors in a role with a high attrition rate, but Tomlin will have to improve upon his career 8.57 ERA at Yankee Stadium. Another storyline in this set could be the return of Andrew Miller (hamstring) from the disabled list against his old club. Miller is eligible to come off the DL on Sunday.