Five things to watch in men's draw

KEY BISCAYNE, Fla. -- Watching the men's side of the tennis tour is like playing the stock market: Some brands are rising in value, others are stalled, and a few are on the decline.

For the past few years, Roger Federer and Rafael Nadal were the best blue chips to invest in. Now, world No. 1 Novak Djokovic has replaced them as the sure-bet to win tournaments.

Federer, Djokovic, Nadal, surging American star John Isner and the rest of the big names will be in Miami this week at the Sony Ericsson Open. Here are five things to watch for:

1. Will Djokovic's roll continue?

Save for two blips over the past two weeks -- losing in the semifinals in Dubai and Indian Wells -- Djokovic has continued to play inspired and consistently tough tennis. He defeated Nadal in a memorable five-set battle at the Australian Open. He's going to be the player to beat in Miami.

2. Federer and Nadal, what's next?

It's hard to lump them together in the same category since their games are very different, but they're in the same boat: chasing down Djokovic. Federer's form has been good; he beat Andy Murray for the Dubai crown and rolled past Isner in the Indian Wells final. But it's still not clear if No. 3 Federer can hang for five sets against the speedy Djokovic and post a win.

Second-ranked Nadal has also had his share of heartbreak against Djokovic. He was crushed after losing that epic final in Australia, giving everything he had but still coming up short. All three players were in the thick of the action at last year's Sony Ericsson, with Nadal beating Federer in the semis and the Djokovic topping Nadal in three close sets for the title. Djokovic has recently had Nadal's number when it's counted most.

3. What's up with Andy Murray?

The forgotten man in many conversations about the top of the men's tennis order is Murray, who is a very quiet fourth-ranked player in the world. Murray pushed Djokovic to five sets in the Australian semis, and then beat Djokovic in Dubai a few weeks ago. He has brought on Ivan Lendl to help his game, and there isn't much clarity yet on how the partnership has improved Murray's game. The results over the past few weeks have been so-so, as Murray was bounced from Indian Wells in the second round. His best result so far this season: reaching the Dubai final.

4. Isner on the upswing?

The lanky American has always had a killer serve, using his 6-foot-9 frame to his advantage. Isner has recently added more consistency and depth in his groundstrokes, allowing him to hang through more than just a hold-serve marathon. He's playing more confidently, coming to net and taking more risks. Isner's win against Djokovic last week was a big one, revealing a complete game beyond the serve. Isner moved into the top 10 for the first time in his career and could be ready to assume the mantle of being the United States' best male player.

5. And then, there's the rest of the crew

Hard-court toughies Andy Roddick (ranked 34th in the world), Jo-Wilfried Tsonga (sixth) and Juan Martin del Potro (11th) could make things interesting for the top seeds. But in the end, this tournament will end up being another episode of the Federer-Nadal-Djokovic show.