Report Card: Juan Martin del Potro quietly shining in 2012

Juan Martin del Potro defended his title at the Estoril Open by dropping No. 2-seeded Richard Gasquet 6-4, 6-2. (Jose Manuel Ribeiro/Reuters) The Report Card

Juan Martin del Potro defended his title at the Estoril Open by dropping No. 2-seeded Richard Gasquet 6-4, 6-2. (Jose Manuel Ribeiro/Reuters)

The Report Card hands out grades for the week in tennis. This past week, Juan Martin del Potro won another title and Sara Errani continued her clay-court winning streak.

Juan Martin del Potro: A. The Argentine successfully defended his title at the Estoril Open without dropping a set, beating Richard Gasquet 6-4, 6-2 on Sunday to extend his 2012 clay record to 6-0 and improve to 27-6 this year. Ranked 11th, Del Potro's six losses this year have come against quality opponents: Roger Federer (four times), David Ferrer and Marcos Baghdatis. So at what point do we set aside our tempered expectations given his comeback from wrist surgery and begin to anticipate more?

Sara Errani: A. By defeating Elena Vesnina 7-5, 6-4 for the Budapest title, the Italian stretched her winning streak on clay to 15 and she heads into Madrid fresh off consecutive titles in Hungary and Barcelona. Errani moved to 16-1 on clay this year and she's dropped only three sets on the surface (not counting the second set of her one clay loss, a retirement at Fed Cup when she was trailing Lesia Tsurenko 1-6, 0-3). Given the quick turnaround, I don't expect too much from her in Madrid, though if she can get past Agnieszka Radwanska in the second round, there's no reason to think she can't make the semifinals. But look out for her when she plays Rome.

Philipp Kohlschreiber: A. The No. 1 German done good in Munich, capturing his second title at the BMW Open, where he knocked off Feliciano Lopez in the semifinals and Marin Cilic in the final. I guess the guy just really loves Bimmers.

Andreas Seppi: A. Two Italian champions in one week? Not too shabby. In a tournament full of journeymen, Seppi came out on top at the Serbia Open, toppling David Nalbandian 2-6, 6-2, 7-5 in the semifinals before beating surprise finalist Benoit Paire 6-3, 6-2.

Kaia Kanepi: A. It's easy to forget that Kanepi was actually the first WTA titlist of the year, winning Brisbane in early January. You forget that because Kanepi failed to sustain her success, going 3-4 since entering last week's tournament in Portugal. But the hard-hitting Estonian finally turned it around in Estoril to win her second title of the year, beating two top 30 players in the process. Will the win jump-start her season?

Tommy Haas: A-plus. What an incredible week for Haas in his native Germany. As a wild card, the No. 134-ranked Haas stunned top-seeded Jo-Wilfried Tsonga and Baghdatis to make the his first ATP Tour-level semifinal since 2009 and first clay semifinal since Houston in 2006.  At 34, Haas is showing he still can pull off the big upset. The question is whether he has it in him to remain consistent throughout a tournament. He clearly ran out of steam in his semifinal loss to Cilic.

Jo-Wilfried Tsonga: D. Not to take anything away from Haas, but come on. The world No. 5 lost quietly in his first match in Munich, going down to Haas 6-1, 6-4. The Frenchman, who outranked the Munich field by more than 10 spots, still hasn't won a clay title in his career and from the look of things, he's stuck playing the uninspired tennis that's plagued him all year.

Francesca Schiavone: F. The tumble continues for the 2010 French Open champion, who dropped to 2-4 on clay in 2012 after losing in the first round of Madrid to Varvara Lepchenko. Last year, Rome served as quite a homecoming for Schiavone, who hadn't played in Italy since her win at Roland Garros. This year? It'll be awkward.

Melanie Oudin: B-plus. Oudin couldn't follow up her win in Charlottesville to secure the French Open wild card outright in Indian Harbour Beach, but she got a little help when Grace Min defeated Maria Sanchez in the Indian Harbour finals to knock Sanchez out of the running. With that, Oudin can book her flights to Paris, having earned a spot in the main draw. She's never won a main-draw match at Roland Garros, but for Oudin it was all about getting there.

Benoit Paire: B-plus. A cult favorite among fans, Paire has always been the guy you love and hate to watch. The hot-headed Frenchman has a beautiful game that's unfortunately coupled with a head that's on the verge of imploding at any given moment. So credit to Paire for a solid week in which he reached his first ATP Tour final, in Belgrade. Ranked No. 96, Paire beat Fabio Fognini, Guillermo Garcia-Lopez, Jarkko Nieminen and top-seeded Pablo Andujar before losing to Seppi in the final. Paire raised his ranking to No. 67.

David Nalbandian: C-plus. He's slim and trim but still trying to find his legs on clay. Nalbandian lost to Seppi in the Belgrade semifinals. I know it's unfair to expect more from a guy who has arguably underachieved through most of his career, but Nalbandian's quarterfinal run in Indian Wells gave me hope that he'd finally rededicated himself and achieve some level of consistency. Maybe he'll pull the pieces together in Madrid or Rome.

Nikolay Davydenko: F. The defending champion crashed out in the first round of Munich to a player ranked No. 210, Robert Farah. Outside of his win over Gasquet in Rotterdam, Davydenko hasn't beaten anyone inside the top 50 all year, losing twice to players ranked outside the top 180.*

Marin Cilic: B-minus. At best, Cilic has come out of his year-long funk and is starting to produce more reliable results. At worst, he's stalled that funk. Either way, Cilic has shown that he's worth talking about again. But he needs the lower-level titles to boost his ranking so that he isn't going up against the top 10 in the early rounds. Cilic did well to get to the final against Kohlschreiber in Munich, but grabbing the title against a less-than-packed field would have been huge for his year.

Ernests Gulbis: B. Good news: Ernie won a match! Bad news: That's news because he hadn't won a Tour-level match since Delray Beach in February.

Juan Ignacio Chela: D. The Argentine sent out a series of tweets mocking the WTA, all of which were offensive. Not necessarily because they were sexist, but because they just weren't funny.

*This post was edited after the initial publish to correct the fact that Davydenko won his first-round match in Madrid.