LEADING OFF: Hurry up, it's opening day! Aces and A-Rod, too

A look at what's happening all around the major leagues today:

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SPEED IT UP

Major League Baseball's new pace of play rules are in effect. We'll see whether Red Sox slugger David Ortiz can stick in the batter's box when Boston visits Philadelphia. Clocks in every ballpark will count down the time between innings.

HE'S BACK

Alex Rodriguez puts on the Yankees' navy pinstripes for the first time since serving a season-long drug suspension. What kind of reception will he receive in the Bronx when New York opens against the much-improved Toronto Blue Jays?

ALL ACES

Big names abound on the mound as World Series MVP Madison Bumgarner, Cy Young winners Clayton Kershaw and Corey Kluber, Felix Hernandez, Masahiro Tanaka and new Nationals ace Max Scherzer make their first starts.

HOMECOMING

Matt Kemp returns to Dodger Stadium with the fresh-look Padres. San Diego went through a major overhaul, getting closer Craig Kimbrel, brothers Justin and Melvin Upton, opening day starter James Shields and more.

BREWERS AND BADGERS

For the first time, 28 teams are opening on the same day. Fans at Miller Park might hurry home to their TVs after Milwaukee hosts Colorado in the afternoon - at night, Wisconsin takes on Duke for the men's college basketball championship.

ROSTER FODDER

The Giants begin the season with the oldest team in the majors - their players are an average of 31, exactly a year older than second-place Kansas City; Texas is the youngest at 27, STATS said. And Atlanta has only six players left from opening day last year, the biggest turnover in the big leagues.