This difficulty is extremely challenging.... and frustrating. It's best to play it with another human, as a lot of times the AI will not be very helpful on defense.
Im finding the most success with LeBron and Shaq, both Gold. You want power dunkers and a big man that can protect the basket. Don't think about shooting threes; the CPU will block you half the time, or you'll just flat out miss them on this difficulty. I managed to make it to the Conference Finals but the deeper you get into the playoffs, the cheaper and more bullshit the computer gets. They will send you into the front row on dunk attempts, you'll inexplicably miss wide open dunks, and even if the opposing team misses a dunk, the other guy will magnetically attach himself to the ball and put it back in, sending your two players to the floor in the process.
My only advice is to just keep playing aggressive. Don't overdo it with steal attempts; the AI seldom gives up the ball. Keep as much pressure on them as you can, don't jump at every opportunity, and on offense, just crossover and dunk as much as you can. Don't hold on to the ball too long; keep the ball moving. The AI will snatch that shit from you quickly and convert it on the other end.
Also, watch the lotto pick for the CPU. If they Curse you, or freeze your basket and you have the lead with under a minute left, play keep away. Manage the shot clock and try to get offensive boards to milk the clock.
UPDATE: I just upgraded Shaq and Bron to Diamond. I'm finding games noticeably easier right now. Its just the regular season, so I'll update this when I start my playoff run. Getting your guys to Diamond might be the key to this.