Robredo beat three of the top four seeded players, including No. 2-seeded Kevin Anderson in Sunday's final, at the Grand Prix Hassan II tournament in Morocco. It was his 11th ATP title but first in more than two years.
The victory also moved him up 29 spots in the world rankings to No. 43.
Isner won the U.S. Men's Clay Court Championship in Houston, stopping top-seeded Nicolas Almagro 6-3, 7-5 in the final. Isner was the runner-up in the event last year. It was Isner's sixth ATP champion, half of which have come in the last year.
But it didn't budge his ranking, leaving him at No. 23 in the world.
There were no changes in the Top 10 as Novak Djokovic notched his 77th week at No. 1. He's within three weeks of Lleyton Hewitt's mark of 80 weeks of leading the rankings. That is ninth most all-time.
Djokovic has 12,500 points in the rankings with Andy Murray second at 8,750 and Roger Federer in third, 90 points back of Murray. David Ferrer (6,970) remains fourth and Rafael Nadal comes in fifth at 6,385.
Tomas Berdych's total of 5,015 is sixth-best while Juan Martin del Potro is seventh at 4,750 and Jo-Wilfried Tsonga eighth at 3,695. Richard Gasquet (3,230) and Janko Tipsarevic (3,000) round out the Top 10.
Djokovic is the top seed at this week's Monte Carlo Rolex Masters tournament. He was runner-up in Monte Carlo in 2012 to Nadal. Berdych and Gilles Simon were the other semifinalists.
Eight of the Top 10 players are entered at Monte Carlo. Federer and Ferrer are sitting out the tournament.