Del Potro's next tournament was the ATP Masters at the 2011 BNP Paribas Open. He reached the semifinals, where he lost to top seeded Rafael Nadal in straight sets. Del Potro then flew to Key Biscayne, Miami to participate in the second ATP Masters of the year at the 2011 Sony Ericsson Open. Del Potro made it to the fourth round, in the third round he defeated world No. 4 Robin Söderling in straight sets, however in the next round he lost to eventual semifinalist Mardy Fish in straight sets.