Cardinals leadoff man Matt Carpenter walked up to the plate, shook hands with the umpire, greeted the Pittsburgh catcher and got comfortable in the batter's box.

Just like that, fans everywhere settled in for a fresh new season.

''Opening day, for me, is sort of like Christmas,'' Commissioner Rob Manfred said at the Toronto-Tampa Bay game. ''It's one of the most exciting days of the year.''

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A World Series rematch in Kansas City and a meeting of NL playoff teams sweetened Sunday's schedule.

It was 39 degrees at PNC Park when Pirates lefty Francisco Liriano threw the first pitch of the season. Hours earlier, the grounds crew cleared ice off the tarp after snow flurries fell.

Liriano did just fine: six shutout innings, 10 strikeouts and an RBI single for the first run of 2016 in a 4-1 win over St. Louis.

All-Star Chris Archer had no weather worries when he started for the Rays under the dome at Tropicana Field. His bigger concern was the Blue Jays - the highest-scoring in the majors last season, Toronto got a two-run single in the first inning from Edwin Encarnacion.

In Kansas City, the forecast was for 70 degrees under a setting sun when the champion Royals hosted the team they beat last October, the New York Mets.

The parking lots at Kauffman Stadium were jammed with tailgaters long before the first pitch, and Royals rooters were eager to see the World Series flag raised in right field.

''It's a fun day to be part of,'' Kansas City first baseman Eric Hosmer said, adding, but once it's over it is, OK, time to get back into the routine.'''

Matt Harvey was set to start for the Mets vs. Edinson Volquez. The faced each other on the final day of 2015 - Game 5 at Citi Field, where the Royals rallied to win the crown.

Fans in KC saw something new, too. There's extra netting behind the plate to protect crowds from foul balls, a recommendation MLB made to all teams during the offseason.

Most every other club starts up Monday. The Tigers and Marlins are the last to open, on Tuesday at Marlins Park.

David Ortiz begins his farewell tour when the Red Sox open at Cleveland in the Boston debut of high-priced ace David Price. Big Papi and Price took it easy Sunday, going across the street from Progressive Field to watch LeBron James and the Cavaliers take on Charlotte.

Plenty of top pitchers were on tap to start Monday, with Zack Greinke, Dallas Keuchel, Clayton Kershaw and Felix Hernandez among them.

NL Cy Young Award winner Jake Arrieta starts Monday night as the popular and talented Chicago Cubs visit the Los Angeles Angels.

''If you factor in everything - experience, talent level, the motivation of the group - they want to become a part of the first team that wins a World Series for the Cubs in a long, long time,'' Chicago manager Joe Maddon said. ''So there's so many good things that can repel pressure and expectations.''

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AP Sports Writers Dave Skretta and Fred Goodall contributed to this report.