Woods (left) has 14 major victories to Els' three
Tiger Woods believes Ernie Els could have reaped the rewards of a tougher rehabilitation programme after major knee surgery in 2005.
Els is currently 20th in the rankings and without a win in 41 tournaments.
World number one Woods had a similar operation on his anterior cruciate ligament (ACL) last year and believes he is approaching his best again.
He said: "I feel pretty good with what I've done, and I think Ernie could have worked a little bit harder."
Speaking ahead of the Deutsche Bank Championship in Boston, the American added: "Ernie is not a big worker physically, and that's one of the things you have to do with an ACL repair.
"But Ernie travels all around the world, more than any other golfer. He plays all over the place, and it's harder for him.
"He is starting to put it together a little bit. We all know he's got the talent, we've seen it. It's just a matter of him getting the confidence in what he's doing."
In 2006, Els - who topped the rankings three times in 1997 and 1998 - spoke about a having three-year plan to grab the number one spot from Woods.
The triple major winner's challenge failed to materialise, although he has shown encouraging form of late.
Els was joint eighth at the Open Championship in July and equal sixth at last month's USPGA Championship
He finishing one shot behind winner Heath Slocum at last week's FedExCup opener, the Barclays Classic in New York.
With his 40th birthday approaching on 17 October, he admitted he no longer has time on his side, but said: "If I keep playing the way I did last week, maybe the three-year plan can be revived.
"I feel positive and feel my game is coming around so I just want to try and win.
"I got a win early last year and then I really didn't hit form at all so it's been an awkward couple of years.
"I don't want to be struggling like I did. There's no worse feeling than to play at a certain level and then drop off, knowing you can do a lot better."
"I hit my low point at the US Open (in June)," added Els, referring to his missed cut at Bethpage Black.
"I just want to get back to where I feel I should be, that's top five in the world at least and winning tournaments."