“You gotta believe!” (“Ya gotta believe!”)

"You gotta believe" (or "Ya gotta believe") was the catchphrase of New York Mets baseball relief pitcher Tug McGraw in 1973. The Mets had come from far behind in a crowded field to win the division, then the National League pennant.

There's no doubt that McGraw used it and popularized it that 1973, but there is still some question as to where he got it and when he first used it.

http://www.jerrygrote.com/tug_mcgraw.htm
Tug McGraw
Frank Edwin McGraw Jr.
Bats Right, Throws Left
Height 6' 0", Weight 185 lb.
Debut April 18, 1965
Born August 30, 1944 in Martinez, CA
Died January 5, 2004 in Nashville, Tennessee

http://www.tugmcgraw.com/HomePage.html
Add November 14, 2005 for the First Annual Ya Gotta Believe Gala Dinner at New York City's Gotham Hall. This will be an exciting event with very special guests who will help the Foundation to celebrate Tug's life as an athlete, entertainer and friend. The evening will feature a reception and dinner and the presentation of several awards that commemorate and honor Tug's "Ya Gotta Believe" legacy.

Baseball's Greatest Quotations
by Paul Dickson
New York: HarperCollins
1991
Pg. 286 "Ya gotta believe."
July 1973 motto and exhortation, used in the Mets' move from sixth place to the National League pennant. (...)

McGraw uttered the phrase after a clubhouse speech by M.Donald Grant while the Mets founder yelled: "He's right! He's right! Just believe! You gotta believe!" (Speculation was that the puckish McGraw was mocking Grant. He probably was, but the expression still became the team's emblem down the stretch.)

31 July 1973, New York (NY) Post, pg. 64:
Tug Ready for Bullpen.
(No YGB - ed.)

1 August 1973, New York (NY) Post, pg. 72:
Mets: It's Dial H for Help
(No YGB - ed.)

3 August 1973, New York (NY) Post, pg. 67:
Tug Wins the War.
(No YGB - ed.)

6 August 1973, New York (NY) Post, pg. 55:
Banner Day? Not for Mets.
Banners: The Mets Stink. So Does This Banner; When the Mets Threat the Other Team Sweats; To Be a Met Is Every Little Leaguer's Dream; We've Got Pennant Fever over Tom Seaver; Let's See the Mets Fold Up; Seems Like Old Times. NL Cellar (Summer Home of Y. Berra); Wait til next year; The last shall be first; The first shall be last; When you say Bud Harrelson, that says it all; The Mets Are Victims of the Energy Shortage; Out of Gas in 1973; Thanks for Sticking With Us.

17 August 1973, New York (NY) Post, pg. 76:
Mets Must Start Thinking.
(No YGB, but the article begins, "This is for those who believe in miracles. Stop believing" - ed.)

28 August 1973, New York (NY) Post, pg. 56:
Old McGraw New Stopper.
(No YGB - ed.)

6 September 1973, New York (NY) Post, pg. 64, col. 1:
There is life in the left arm and voice of Tug McGraw, silent for so long.
(No YGB - ed.)

10 September 1973, New York )NY) Post, pg. 54, col. 4:
Now they believe they can win it.

19 September 1973, Daily News (New York, NY), pg. 106, col. 1:
Despite what you may have read or heard, somebody up there likes Yogi Berra. And you better believe it.

21 September 1973, New York (NY) Post, pg. 79, col. 3:
(No YGB, but catcher Ron Hodges says, "This is all so unbelievable; I can't believe it's happening and that I'm a part of it. (...) I just can't believe it all." Mets beat rival Pittsburgh in 13th inning - ed.)

22 September 1973, Daily News (New York, NY), pg. 28:
(No YGB, but real close. Phil Pepe writes that "It's 1969 all over again." He uses "It's unbelievable" or "unbelievable" about a dozen times. This is one paragraph that's very close - ed.)
Unbelievable
But with only eight games to play, you have to believe in the Mets. You have to believe they have enough to carry on. You have to believe because they have made you believe.

24 September 1973, Daily News (New York, NY) , pg. 66, col 5:
The Miracle of Flushing will be if the Mets DO NOT win the pennant.

A sign popped up in the bottom of the first inning yesterday with the Mets losing, 2-0; it read "You Got to Believe." It was held by two nuns.

24 September 1973, The Journal-News (Rockland County, NY), "Miracle or not, ya gotta believe" by Don Drumm, pg. 6B, col. 1:
NEW YORK -- "You gotta believe."
(...)
The slogan popped up on a sign held by two nuns in the box seats who have been following the Mets all year and watched them climb from the cellar, 12 games out, to first place.

2 October 1973, Daily News (Ne York, NY) , pg. 3, col. 1:
...Tug McGraw stood on a makeshift platform, shouted,
'One...two...three...you gotta bee-leeeevvvvve!'

Pg. 40 (photo caption):
"You gotta believe," yells Tug McGraw after
saving Tom Seaver's win for flag.

Pg. 68, col 3:
McGraw remembers a day in July, when things were at their lowest. It was July 11. He remembers because that's the day Bud Harrelson and Jerry Grote came off the disabled list.

"Ya Gotta Believe"

"I was kidding around with the fans before the game," Tug said. "I was telling them, 'You gotta believe.' It was at the lowest point in my life, but I kept saying to myself, 'You gotta believe.'"

He picked it up from Father Feehan, his baseball coach at St. Vincent's High in Vallejo, Calif. "He would always say, 'You gotta (sic) believe in yourself.' He's dead now, but I still talk to him. In my dreams."

McGraw had been having fun with the fans that night of July 11. Then M. Donald Grant, chairman of the board of the Mets, called a clubhouse meeting.

"He need almost the same words I had been using (sic)," Tug said. "He told us we had to believe in ourselves. That's when I shouted, 'You gotta beeeleeeeeeve.' I was afraid Mr. Grant might think I was mocking him, so I had a talk with him and told him I wasn't making fun at him."

Soon, McGraw's "you gotta beeee-leeeeeeeeeeeeeevvvvvvve" became the team's rallying cry, and last week in Shea, when the Mets were driving to the top of the NL East, two nuns showed up carrying a sign that said: "You Gotta Believe."

(NOTE: There are errors here: the M. Donald Grant meeting wasn't July 11th. The meeting was July 9th and reported on July 10th -- and I didn't see YGB! The Mets were in first on September 21, Phil Pepe called it "unbelievable" on September 22, and the nuns came out with a "You Got to Believe" (not "You Gotta Believe") banner on September 23. If Tug McGraw had been saying it all along since July 9th or July 11th, why didn't it show up in July, August, or September stories? - ed.)