To understand how Patrick Mahomes, 23, could remain so composed on his rocket-ship rise to stardom is to know his family's history when it comes to big games and the poise required to win them.

Nearly two decades before Mahomes and the Kansas City Chiefs started preparing to face Tom Brady and the New England Patriots in the AFC Championship Game, Mahomes' father, Pat, was as nervous as a pitcher could be while waiting for that phone to ring in the New York Mets' bullpen. But once it did ring, and once the caller requested his services, everything changed.

"That's what you live for," Mahomes recalled. "That's what you dream about as a child, to go in there in pressure situations and perform at the highest level."

Patrick Mahomes' father, Pat, pitched in the major leagues for 11 seasons. Ezra O. Shaw/Allsport

The Mets had lost eight of nine games at the end of September 1999, a collapse that appeared certain to cost them their first postseason appearance in 11 years. Their manager, Bobby Valentine, assured his players they would still make the playoffs if they could just rediscover the belief they had in each other. The Mets would need to sweep Pittsburgh in the season's final series for a shot at advancing, and Valentine trusted few Mets more than he trusted Mahomes, a fearless 29-year-old righthander who was about to make the biggest pitches of what would be an 11-year career.

"For the first time in my life I had a manager who totally believed in me," recalled Mahomes, who had already pitched for the Twins and Red Sox, and for the Yokohama BayStars in Japan. "Bobby was the first manager who let me be me on my mound."

Valentine also let his reliever bring his 4-year-old son to work. Mahomes had one of the Mets' clubhouse guys put together a uniform for young Patrick, who was allowed on the field during batting practice.

"An adorable kid," Valentine said. "I recall Patrick running around in my clubhouse, jumping up and giving guys high-fives after games. During batting practice Pat would take him into the outfield behind second base."

Some coaches warned Mahomes that he needed to guard his son as line drives were whistling all over Shea Stadium, but the pitcher thought Patrick already knew how to handle himself on a ballfield. Pat and Patrick used to play a game called 500 that earned a participant 25 points for fielding a ground ball, 50 for fielding a one-hopper, and 100 for catching a fly ball. Patrick figured he needed to run down some 100-pointers during BP if he wanted to finally defeat his dad. He was 5 years old in the 2000 season when he caught his first big-league fly, off the bat of Robin Ventura. "I can still remember him holding up the ball, all excited," his father said.

But back in the fall of 1999, times were tense at Shea. On the night of Oct. 1, the Mets and Pirates had tumbled into extra innings when Valentine asked Mahomes to face the middle of the Pittsburgh order.

"Pat Mahomes never shied away from the baseball," Valentine said. "He wanted to be center stage."

The reliever surrendered a leadoff single in the 10th, and after a sacrifice bunt and intentional walk put the Mets' season on the brink, he answered by retiring the next two batters and then pitching a 1-2-3 inning in the 11th.

Pat Mahomes thinks his son learned a lot being raised around major leaguers. Courtesy the Mahomes family

The Mets won on a Ventura single, and Mahomes left the building with an 8-0 record. Two days later, with the Mets needing a victory to ultimately force a play-in game against Cincinnati for the wild card, Valentine called on his reliever with the perfect record in the sixth inning of a 1-1 game. With two on and two out and the Pirates' most dangerous hitter, Kevin Young, at the plate, Mahomes stared down the consequences of a 3-2 count, channeled the energy delivered by 50,000 screaming fans, and struck out Young swinging in arguably the biggest out in the Mets' 2-1 victory.

"Pat had that magic going for him," Valentine said. "We were always looking for ways in '99 to get him in the game, because when he got in the game, we won."

The Mets beat the Reds to earn the wild card, beat the Diamondbacks in the division series, and then faced the 103-win Atlanta Braves in the National League Championship Series. Down 0-3 in that NLCS, the Mets rallied at Shea to force a Game 6 in Atlanta that was immediately imperiled by starter Al Leiter, who gave up four runs in the first inning before Valentine summoned Mahomes with runners on first and third and one out.

Mahomes allowed a sacrifice fly before getting Walt Weiss to ground into a double play. "And as I walked off the mound," the reliever recalled, "I was yelling at the dugout, 'I'm going to keep it right here. Just score some runs. I'm going to keep it right here.'"

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Mahomes pitched four scoreless innings, and the Mets turned a 5-0 deficit into an 8-7 lead before the Braves prevailed in the 11th and advanced to the World Series. The following year, Mahomes went 5-3 for the Mets but struggled late in the season and, after his ERA was irreparably harmed by one dreadful outing, was left off the postseason roster. Valentine remembered that it was a close call, that there were extensive conversations among team decision-makers about Mahomes and whether he should make the cut, and that Valentine supported his reliever in those conversations.

"I always felt I could count on Pat," the manager said. "He was one pitch short for a starter, but he was the perfect long man and a godsend for us. He could throw every day, he was a great athlete for a pitcher, and a joy to have on the team. His fastball was pretty straight and it got caught a couple of times, but you always wanted someone on the mound who wasn't afraid. And Pat was never afraid in big games."

The Mets lost the 2000 World Series to the Yankees in five, and Mahomes still believes he could've made a difference in that outcome. "But I think we lost that World Series when Roger Clemens threw the bat at Mike Piazza (in Game 2)," he said. "Honestly, we should have been out there fighting the Yankees and letting everyone know we were invested. Being that we didn't get into a fight that night, they gained a little momentum and we could never get it back."

All these years after failing to get his crack at the Yankee dynasty, Pat Mahomes is planning to be in Arrowhead Stadium on Sunday to watch his son get his crack at the Patriot dynasty. Pat thinks Patrick learned a ton from growing up around major leaguers, from joining Alex Rodriguez during BP and from taking grounders with Derek Jeter. Pat thinks Patrick learned a lot from being on the World Series field as a 5-year-old, shagging fly balls before those Mets-Yankees games, even though his old man wasn't on the active roster.

Patrick Mahomes roamed the outfield with pitcher Mike Hampton during practice at Shea Stadium before Game 3 of the 2000 World Series. AP Photo/Kathy Willens

"There aren't many events bigger than the World Series," Mahomes said. "That's why I don't think any moment now is ever too much for Patrick."

Once upon a time, the father thought the son would someday play October baseball. Pat's fastball was clocked at 92 mph in high school, and Patrick's topped out at 95 mph. The son would've been a big-throwing, big-hitting outfield prospect, and maybe an early-round pick in the 2014 major league draft, had Patrick not made it clear to teams that he wanted to chase his quarterbacking dreams. He put up video-game numbers at Texas Tech, and then in 2017 was drafted 10th overall by Kansas City, where his father had signed in 2006 before pitching for the Royals' Triple-A team in Omaha.

Patrick might already be the best player in the NFL, and the best player from Tyler, Texas, since Earl Campbell. His father used to tell Patrick that he reminded him of Steve McNair. After the Chiefs drafted his son, Mahomes said he saw Patrick as a cross between Ben Roethlisberger and Aaron Rodgers.

Valentine, now the athletic director at Sacred Heart University in Connecticut, calls his former pitcher's son "the most special athlete I think I've watched in any sport in recent years, or maybe in my lifetime." Valentine said he gets goosebumps when the TV cameras show Pat Mahomes in a stadium box watching Patrick play.

As a tribute to his dad, Patrick Mahomes wore a No. 23 Mets jersey to a Sunday night game in October against Cincinnati. AP Photo/Ed Zurga

The quarterback was good for 50 touchdown passes, more than 5,000 yards, and a playoff victory over Andrew Luck in his first season as a starter -- the Chiefs' first home playoff victory since Joe Montana was under center. And yet his father's proudest moment unfolded in October, when Patrick wore Pat's old Mets jersey, No. 23, to his Sunday night game against Cincinnati.

"That let me know that all of his hard work, and all the late-night hours we put in together, had paid off," Pat said. "He wore it as a tribute to me, and to what I was able to do in prime-time games under pressure."

Three months later, Patrick Mahomes will pay tribute to his father by taking the field on a brutally cold Kansas City evening to face the greatest quarterback of all time. If the Chiefs advance to their first Super Bowl in nearly a half-century, at least one fan is going to party like it's 1999.