Joe Montana helped the 49ers win Super Bowls after the 1981 and 1984 seasons. But first-round playoff exits in 1985 and 1986 coupled with Montana's back surgery led to the team's acquisition of Steve Young from the Buccaneers in 1987. That created the greatest quarterback controversy in NFL history as it lasted until Montana was traded to the Chiefs before the 1993 season. The two men couldn't have been more different in background, personality, and playing style, and their competition created as much tension as it did greatness, forcing Montana to prove that he was still the game's best quarterback and Young to prove that he was a worthy successor. Adam Lazarus takes readers into the locker room and inside the huddle to deliver the real story behind the rivalry in Best Of Rivals. Here is an excerpt:

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Montana and Young brought disparate skill sets and outlooks on playing the position of quarterback to the field. Methodically picking apart the opposing defense with deadly precision, while occasionally sidestepping -- not necessarily running away from -- the pass rush enabled Montana to bring a pair of Super Bowl trophies to San Francisco. Young, a left-handed passer who struggled mightily with accuracy in his first few seasons with the 49ers, was impatient in the pocket, eager to tuck the ball, employ his running back–like skills, and engage linebackers and defensive backs, rather than avoid them.

The difference in their athletic strengths and weakness, however, couldn't compare to the difference in their backgrounds and demeanors.

In every way imaginable, Montana epitomized his nickname, "Joe Cool."

On the football field, he was never rattled, whether in the face of a blitzing linebacker or a twenty-eight-point halftime deficit. And out of uniform, the bluecollar Catholic Western Pennsylvania product, was equally relaxed, as he drove one of his sports cars -- by the late 1980s Montana owned a Corvette, a BMW, a Mercedes-Benz 500 SEC, a Porsche 928, a Ferrari 308, and a Ferrari Testarossa -- off to go and have a beer with or play practical jokes on his buddies.

Young -- a Mormon from Connecticut who despite millions of dollars in the bank drove a beatup 1965 Oldsmobile Cutless until it died with more than 270,000 miles on the odometer -- displayed an unwavering intensity.

Teammate and Pro Bowl guard Guy McIntyre, later characterized Young as "nervous" in the huddle.

"I think a sense of urgency is a great way to describe him," said Brent Jones, Young's road-trip roommate. "There were even times when I would be like, ‘Relax, we're up by a couple touchdowns, have some fun, enjoy the moment.' And I think that that was not necessarily built into his mindset. ... One of the things we used to talk about was ... look around, take in the moment, appreciate your teammates, look at the coaches, look at the fans, they're cheering for you, be aware of that, because sometimes he was so siloed and so focused that he'd miss out on some of the more exciting things that were going on."

Still, contrasting playing styles and even the contrasting personalities alone were not enough to create a quarterback controversy worthy of national interest. For that to happen, another element was necessary.

"People always think that we fought," Young said years later. "We never had a cross word, never had an argument, and I've always said to people that it went as well as it possibly could with two hypercompetitive people. But it wasn't easy; it was difficult, difficult for both of us."

"It's not that there was bad blood," Montana said in 2011. "I guess the only way you can explain it is if you go to work every day in an office ... you're not always best friends with the guy sitting next to you. You're friends, but you're not best friends. And while we were friends, we wouldn't hang out together. ... It had nothing to do with the game or the competition; it's just our personalities are different."

At the time, the way in which both Montana and Young spoke about the issue through the press only stirred up more friction.

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"I remember in training camp that year, Steve refused to call himself the second-string guy," Brent Jones remembered. "He even made a quote, and I'm sure this didn't go over well with Joe, but he said, ‘I'm 1-B.' So there's 1-A [Montana] and 1-B [Young]."

During that same training camp, Montana attempted to explain his relationship with Young as segregated: personally it was amicable; professionally, that was another matter.

"We're friends, Steve and I," Montana told Sports Illustrated's Ralph Wiley. "But out on the practice field, if he doesn't hate me as much as I hate him, then there's something wrong."

There was already an innate discord between the two -- an aging, battered legend trying to fend off the advances of a younger, stronger challenger -- so Montana's use of word "hate," or Young staking his claim to the starter's job, was provocative.

"[Joe] was so competitive -- and you know players will try to beat each other at Tiddlywinks -- it was such an affront to him," Young's agent, Leigh Steinberg remembered. "It really put a tension, suspicion, distrust, into that relationship between Steve and Joe from the start. Steve was like the younger brother who venerated Montana and loved Joe. Joe was a proud competitive incumbent who didn't want Steve there."

Even within the confines of the team's facilities, passive-aggressive warfare was employed. Both lobbied for more repetitions in practice, then complained to third-string quarterback John Paye while their competition ran the offense.

And when Paye wasn't either man's confidant, the media was.

That season, a member of the press was pulled aside by Montana, who said that Young had covertly erased portions of practice film in which Young threw a bad pass or made the wrong read. Within a week, Young pulled aside that same person to inform them that Montana was spreading false rumors about him erasing practice films to hide mistakes from the coaching staff.

"As a journalist, you're like, ‘Well, this is really great for people like me,'" the member of the press later recalled. "But are we in junior high, or what's the deal? ... I still can't really believe that those two guys, that accomplished, did that. But that was the atmosphere."

-- Excerpted by permission from Best Of Rivals by Adam Lazarus. Copyright (c) 2012 by Adam Lazarus. Published by Da Capo Press. All rights reserved. No part of this excerpt may be reproduced or reprinted without permission in writing from the publisher. The book is also on sale at Amazon. Follow Adam Lazarus on Twitter @lazarusa57.