What made Billy Martin so great was also what made him so volatile: his intensity. It allowed him to give a kick start to his teams, yet made it so difficult to keep it going.
Billy Martin was the most fearless manager in baseball history. In 20 years of managing, he never backed down from a challenge. As has been well documented by others, Martin consistently caused dramatic improvements to his squads immediately upon arrival by pushing them hard...
Martin's approach had its downside. He pushed his teams so hard they could not keep up with his pressure. Hiring Martin was like pushing too much voltage through a light bulb: for a brief while it burns brighter than otherwise possible, but it soon shatters unless the excess electricity is removed. Despite his impressive starts, Martin never lasted longer than three years in any managerial stint.
Imagine Mike Scioscia, then triple his aggressiveness -
The ultimate Billyball moment came on May 18  when both [Cesar] Tovar and [Rod] Carew stole home plate in the same inning - in the same at-bat. Carew stole his way around the bases in that plate appearance. At the plate during this maniacal base running was Harmon Killebrew. Harmon Killebrew! It boggles the mind: With one of the greatest home run hitters of that or any other generation up Martin wanted his men running wild.
We would never see a manager like that today. Too much research has been done to show how reckless stealing bases can be (especially stealing home).
However, Martin knew what he was doing -
Therein lies the rub. Instead of getting worse, his teams got dramatically better despite all these reckless maneuvers.
Once Martin had installed the desired mindset in Minnesota, there was no need to run the risky home plate steals. For the rest of the season opponents played back on their heels, wondering what Minnesota would do next.
Is it worth it to have base-runners play extra-aggressively early in the season if it affects opponents throughout the year? Say an inordinate number of attempted steals happen early on, would that cause defenses to play closer to the bases, opening larger holes for the hitters? And if so, would it make up for the base-runners that got caught?
I don't know the answer, but it's food for thought.
In addition to being aggressive with base-runners, Martin was also one of the hardest managers ever on pitchers -
He would do whatever it took to win that day, and not worry about any possible negative side effects in the future. The best example came when he ran the A's in the early 1980s. They had a great stable of young pitchers whom Martin pushed as hard as he could. In 1980, they completed 94 games, the most by any team since the 1940s.
In 1981, the A's completed "only" 60 games, but a third of the season was lost to a strike. In fact, no other team of the 1980s completed that many games, despite Oakland only playing 109 games.
In the short run, it worked as Oakland produced the AL's best record in 1981. Then the A's pitchers' arms fell off and they lost 94 games in 1982. Martin never considered the long-term repercussions. Then again, it was the only time he lasted three full seasons as manager. Martin was so concerned with seizing the day that he never considered what would happen tomorrow...
Martin handled his relievers similarly. He wanted whom he wanted when he wanted them without concern toward keeping their arms well rested. As a result, his bullpens consistently ranked among the league leaders in most innings pitched by men with zero days rest.
(For all those saying 'take the leashes off' Joba and Hughes, it's been shown time and again that pushing pitchers too hard, especially young ones, is often detrimental to their long-term effectiveness. In other words, the Yankees know what they're doing, and it's better to be cautious than aggressive with potential future All-Stars. There's a reason Andy Pettitte and Mo Rivera are still pitching well in their late-30s: they weren't abused as youngsters.)
Martin was clearly not a perfect manager, but for a 'win-now' team, he may have been the best.