It was a landmark in television comedy. TV Guide ranked it the fourth best television episode of all-time. And its special guest star was a recently retired MLB first baseman.

What Keith Hernandez did not know about his historic Seinfeld performance in 1992 was that Larry David and the writers had a backup plan if he flopped.

In a recent interview with Rolling Stone, Hernandez broke down the chronology of his appearance in "The Boyfriend." In fact, it was not Hernandez, but his young agent, Scott Boras, who first made contact with Seinfeld. Hernandez had just retired and was reluctant to go into acting. The persuasive Boras told Hernandez he would get limited lines, a first-class flight to L.A. and a generous salary, so Hernandez obliged.

When he got his part, anxiety set in:

"They FedExed me the script, and I saw I had lots of lines. I thought 'Holy s---, I'm can't do this!' So I kind of got a head start on it, because I was mortified. I memorized everybody's lines in every scene I was in. I knew when they were going to speak, when it was my turn, all that. I was really nervous before we shot in front of the live audience, and Jerry turns to me and went 'What the hell are you nervous for? You play in front of 50,000 people.' And I said 'Well, I don’t have to memorize lines when I'm playing in front of them.'"

Hernandez became a guest star legend for his role. The two-time World Series champion, NL MVP, NL batting champion, five-time All-Star, two-time Silver Slugger Award winner and 11-time Gold Glove Award winner befriends Jerry, a die-hard Mets fan in real and fictional life. When Jerry introduces Hernandez to Elaine, the lefty expresses interest in her and sets a date.

Meanwhile, Kramer and Newman animate a story to Jerry in which Hernandez spit on them after a Mets game. When Hernandez hears the story, he recalls it was Mets relief pitcher Roger McDowell, not Hernandez, who spat on the duo.

Hernandez, who is currently a Mets television commentator for SNY in New York, nailed his performance. He later appeared in a Law & Order episode, the Seinfeld series finale, movies "The Scout" and "The Yards" and a series of television commercials, including this Just for Men ad with Walt Frazier:

It turned out the writers and producers had a backup plan if Hernandez's nerves got to him. If the memorable performance was average, Hernandez could have seen his scene cut. The hour-long double-episode could have been a single episode, with a greater emphasis on George Costanza's subplot.

Hernandez revealed what he was told after-the-fact:

"I guess they liked it, because they used it during sweeps. But after I was done, [executive producer] George Shapiro told me they had written in an extra subplot just in case I was unsatisfactory. It was George going for unemployment benefits, the whole 'Vandelay Industries' thing. So, with those scenes, it turned into an hour-long show. If I was bad, it was only going to be a half-hour."

Hernandez delivered. The episode aired for an hour and we now enjoy phrases like "The Second Spitter," "The Magic Loogie Theory," "Nice game, Pretty Boy" and "I'm Keith Hernandez" in our daily vernacular. For the dream team of Hernandez, Boras, Seinfeld and David, it all worked out.

On a side note, this past weekend, the Brooklyn Cyclones, the Mets' short-season A affiliate, held a promotional night to commemorate the 25th anniversary of the first airing of Seinfeld. MCU Park was renamed Vandelay Industries Park for the day and Hernandez bobblehead dolls were given away, among other things:

Oh, and while we are on this topic, the Twitter/Instagram account @Seinfeld2000 teased new Seinfeld emojis this week:

Where's the Magic Loogie, though?

-- Follow Jeffrey Eisenband on Twitter @JeffEisenband.