With the US Open Series on the horizon, here is a look back at a clay tournament in Europe and a hard-court event in South America.

Breakthroughs for 33-year-old Victor Estrella Burgos, 17-year-old Alexander Zverev

Two players on opposite ends of the career spectrum reached their first career ATP semifinals last week. Victor Estrella Burgos, who is now ranked at a career high of No. 82, did so in Bogota. His path included straight-set victories over Juan Ignacio Londero and Peter Polansky before a 6-3 6-4 upset of top seed Richard Gasquet that shocked everyone. Estrella saw his run end after losing two out of three tiebreaks to eventual champion Bernard Tomic, but he had a tremendous week. For a player primarily known for his skill on clay, reaching his first career semifinal on a hard court was even more surprising. Estrella is a testament to the fact that hard work and determination can result in a player succeeding on the ATP World Tour level, even without being stunningly talented. Estrella is currently unsponsored, but brands would be wise to pick him up. He is the top man from the Dominican Republic, and their most successful pro tennis player in history already.

Alexander Zverev announced himself on the ATP stage this week with a semifinal in Hamburg. The 17-year-old will now be ranked in the top 170, and he is the first player of that age to reach an ATP semifinal in several years. The German wild card and former top junior had wins over Robin Haase, and seeds Mikhail Youzhny and Santiago Giraldo this week. He also notched a quarterfinal win over Tobias Kamke before being steamrolled by David Ferrer in the semifinals. Zverev showed mental fortitude well beyond his years, and he already has a Challenger title this season. It should also be noted that he never had won an ATP main-draw match before defeating Haase in the first round.

Ivo Karlovic falls to 0-4 in ATP finals this season

Karlovic has made ATP finals this season on all surfaces, but he has yet to win any of them after losing in Bogota to Bernard Tomic. Karlovic lost to Kei Nishikori in Memphis, Philipp Kohlschreiber in Dusseldorf, and Lleyton Hewitt in Newport in addition to the loss in Bogota. He has been repeatedly points away from victory, having lost second-set tiebreaks to Nishikori and Kohlschreiber and third-set tiebreaks to Hewitt and Tomic. Still at the age of 35, his ability to continue to produce results at the highest level is a testament to his tenacity.   

Bernard Tomic wins first ATP title outside of Australia

Tomic improved to 1-1 in ATP finals this season and won his first title since January 2013 in Bogota. He had fallen out of the top 100, but he will now return there and will be ranked at No. 70. The victory in Bogota was his first outside of Australia, and he had an inspired week overall. Now, we will get to see what Tomic can do in the US Open Series. He was a wild card in Bogota because of his rank but he should have direct entry into ATP tournaments for a while.

Alexandr Dolgopolov joins Nicolas Almagro, Tommy Haas, and others withdrawing from the US Open

Dolgopolov suffered a knee injury in Hamburg that is likely to require surgery, and he joined Almagro, Haas, Juan Martin del Potro, and most likely Ivan Dodig among men who almost certainly know that they will be absent from the US Open Series and US Open. Dolgopolov was having a good season overall, and it’s a shame we won’t get to see him until the Asian swing.

Dusan Lajovic and Lukas Rosol continue success

Dusan Lajovic has had a career year, in what has turned into his first year consistently competing at the ATP level. He reached the quarterfinals in Hamburg after reaching the quarterfinals in Bastad last week. He has also had good results in all three majors this season, highlighted by a fourth-round showing at the French Open. Lajovic is likely the next big Serbian player, already their second highest-ranked man behind Djokovic.

Lukas Rosol also reached the quarterfinals in Hamburg after reaching the final In Stuttgart. The Czech is having much more success in this part of the season than he was last year, when he endured a horrendous losing streak that lasted 10 matches. He has turned into a reliable top-50 player who can compete with quality opponents on a week-to-week basis.

Upset of the week: Hamburg R2 Dustin Brown d. Fernando Verdasco 4-6 6-2 7-6(8)

Dustin Brown fired nine aces and upset the more accomplished clay-courter Fernando Verdasco early in Hamburg. Verdasco only converted three out of 10 break point chances, and though he won four more total points in the match, it wasn’t enough to prevent the upset. 

Dustin Brown fired nine aces and upset the more accomplished clay-courter Fernando Verdasco early in Hamburg. Verdasco only converted three out of 10 break point chances, and though he won four more total points in the match, it wasn’t enough to prevent the upset.