"I think it was great quality tennis, the final set was there were some amazing points. Sorry to Juan Martin, an amazing opponent and player. In some ways he deserves to go through too," Nadal told the BBC after the match.
"Anything could happen, so this is a big achievement for me to get to the semi-finals at Wimbledon."
Nadal, the No. 2 seed, won the first set before dropping the second to his Argentine counterpart. The Spaniard also lost the third set, before rallying in the final two sets to take the match. The final score line read 7-5, 6-7, 4-6, 6-4, 6-4 in favor of the 17-time Grand Slam champion.
The duel lasted 4:48 at Centre Court, the longest match of the tournament this year at the All England Club. After the match, Nadal and del Porto embraced.
"At the moment I'm feeling sad," del Porto told reporters. "After almost five hours of running and playing at this high level against the No. 1 in the world and lost, it's not good for me. But maybe after tomorrow when I get home and I watch the match, I will be glad ... I think Rafa, in the end deserves to win once again."
Nadal battles Novak Djokovic Friday in the Wimbledon semifinals. South African Ken Anderson -- who upset top seed Roger Federer on Wednesday -- battles American John Isner in the other semifinal matchup at the All England Club.
Djokovic is 26-25 in his career against Nadal, but Nadal has claimed victories in their last two meetings. The Spaniard fell to the Serbian in their last Grand Slam matchup, a three-set duel in the 2015 French Open quarterfinals. Djokovic and Nadal have a 1-1 head-to-head record at Wimbledon.