Del Potro is ranked No. 5 in the world but set a goal of cracking the Top 3, which would improve his previous best ranking of No. 4, reached in January 2010.
Del Potro, who was 545 points out of third last week, is just 225 points back of Ferrer and 145 behind Murray. Del Potro was ousted in the third round of the Australian Open in 2013. Murray was a finalist last year and Ferrer lost to Novak Djokovic in the semifinals in Melbourne, so they have to protect more points. That could provide an opening for del Potro to make up additional rankings ground.
There were no changes in the ATP Top 10 as the year's first tennis major opened Monday.
Del Potro defeated defending champion Bernard Tomic -- who draws Nadal in the first round at the Australian Open -- in the Apia International final. That dropped Tomic five spots in the rankings to 57th.
John Isner won the Heineken Open and improves one place to 13th in the rankings. His finals opponent Lu Yen-Hsun goes from No. 61 to 53rd.
The ATP Top 10, listing player's name, home country and rankings points:
1. Rafael Nadal, Spain, 13,130
2. Novak Djokovic, Serbia, 12,260
3. David Ferrer, Spain, 5,640
4. Andy Murray, Great Britain, 5,560
5. Juan Martin Del Potro, Argentina, 5,415
6. Roger Federer, Switzerland, 4,355
7. Tomas Berdych, Czech Republic, 4,180
8. Stanislas Wawrinka, Switzerland, 3,890
9. Richard Gasquet, France, 3,140
10. Jo-Wilfried Tsonga, France, 3,065