Watch List: John Isner, Mardy Fish headline Houston field

Mardy Fish has a 10-8 singles record in Houston including winning the event in 2006. (David J. Phillip/AP) The Watch List spotlights the must-know storylines

Mardy Fish has a 10-8 singles record in Houston including winning the event in 2006. (David J. Phillip/AP)

The Watch List spotlights the must-know storylines for the upcoming week in tennis. This week, while many of the top men and women are resting up for the heavy part of the clay-court swing, two top stars should have quite a homecoming: John Isner and Caroline Wozniacki.

• Houston: BREAKING NEWS: Americans are not allergic to clay. We learned that pretty quickly over the weekend when Serena Williams destroyed the field in Charleston and Isner continued to show what he's capable of on the dirt, beating Gilles Simon and Jo-Wilfried Tsonga in Davis Cup. Now, Isner is flying back to the United States to play in the Men's Clay Court Championships in Houston, a tournament he says he loves. Houston will also see the return of its top seed, Mardy Fish, who missed Davis Cup due to exhaustion but remains in the draw. Overall, it's a strong field for an ATP 250, with Feliciano Lopez, Miami semifinalist Juan Monaco, James Blake, Ryan Harrison and Sam Querrey also in the mix.

• Copenhagen: Welcome to Copenhagen, home of the Caroline Wozniacki Invitational, also known as the e-Boks Open. It's Wozniacki's home tournament, and the only hard-court tournament in Europe that takes place during the clay season. She's obviously the top seed, and while the field is generally pretty weak (the last direct acceptance into the main draw went to Laura Robson, ranked No. 123), there are a few names that are worth watching. Jelena Jankovic, who still hasn't won a match since February, is there trying to jump-start her year, and Angelique Kerber, who has had a strong season (No. 5 in the Race rankings), will try to derail Wozniacki's coronation.

• Barcelona: For those journeywomen who don't want to delay their clay-court preparations in Copenhagen, there's Barcelona. The 2010 French Open champion, Francesca Schiavone, who has been quiet all season, has a load of points to defend during the clay season and she'll start in Barcelona. Schiavone is probably hoping that the red clay will be the magic dust she needs to get herself back into relevancy. She's 4-7 since Brisbane and beat just one top 70 player during that stretch. You get the sense that if she can't back up her 2011 clay season, where she made the Rome quarterfinals and French Open final, the soon-to-be 32-year-old might start seriously considering retirement. Also keep an eye on 18-year-old Garbine Muguruza Blanco, who did well to make the fourth round of Miami. Julia Goerges, Dominika Cibulkova and Sloane Stephens are also in the draw.

• Rafa's knees: Since withdrawing from Miami with tendinitis in his left knee, Rafael Nadal has been resting and recuperating in Mallorca under doctor's orders and hopes to return to practice on Wednesday. That gives him about a week to prepare for his defense of Monte Carlo, a tournament he's owned for seven straight years. Unfortunately for him, Novak Djokovic has decided to enter this year, which means more pressure on Nadal to get fit and into top shape as he tries to win Monte Carlo for a mind-blowing eighth straight time.

• Serena's schedule: After she won her first title on clay since 2008, I asked Williams whether her dominant week made her want to return to the practice courts or try to keep her momentum rolling and play more tournaments. "I definitely want to play more tournaments," she said, "but unfortunately I can't, so my next event will be in Madrid." It was an interesting response -- particularly because she said "I can't" -- given the fact that she said earlier in the week that she was considering playing Stuttgart.