Former world No. 4 Greg Rusedski used the word "incredible" to describe Scot Andy Murray's far tennis achievements. Murray, 30, has been one of the most successful tennis players in the last decade or so. The Scot is a member of the well-known Big Four group, which includes the greats Novak Djokovic, Rafa Nadal, and Roger Federer.

Three-time Grand Slam champion Murray has two Wimbledon titles and one US Open championship in his collection. Murray's collection also includes back-to-back Olympic titles -- London and Rio de Janeiro. 2015 Davis Cup champion Murray went all the way at the ATP World Tour Finals a year ago to claim his maiden title at the prestigious event.

The Scot also fulfilled his long-awaited wish of becoming the world No. 1 at the end of the 2016 season.

"He’s accomplished so many wonderful things in getting to world no 1, winning multiple slams and two gold medals, which is incredible," Rusedski claimed at the National Tennis Centre in Roehampton, per Metro UK.

Murray's health of key importance

Rusedski believes it will all look much better for Murray when he gets his health back to 100 percent. Murray has had a catastrophic season so far, as the injury-plagued Murray is having one of his worst seasons since he turned pro.

Murray hasn't won any Grand Slam or Masters 1000 titles this year. His only title of the year came in Dubai in February.

The Scot's year includes many surprising early exits and surprising losses.

However, Murray was unable to perform at his best. The 30-year-old managed to shrug off shingles and an elbow injury earlier this year. But he has yet to overcome a hip injury. The two-time Wimbledon champion hasn't played since losing in the Wimbledon quarter-finals to USA's Sam Querrey this past July.

"Now it’s about Andy being healthy. The minute he is healthy, that will allow him to get back winning and that is the key to his future success," Rusedski opinioned.

Murray not done yet

Rusedski would love to see Murray do the same things as Nadal and Federer did. Nadal and Federer have been dominant forces this year. After a couple of not so great years, Nadal and Federer resurged big-time in 2017.

Federer quit the 2016 season post Wimbledon as he took his time off to get his health back. Nadal also didn't finish the season as he saw that he simply needed to take a break. The two greats both won two Grand Slam titles this year. World No. 1 Nadal made a comeback to the top of the rankings, while Federer follows him at No. 2.

Murray could end up having a six-month break just as Federer did a year ago. Murray hoped to continue his season sometimes after Wimbledon but that has yet to happen. Should Murray call it a season -- which seems likely -- he would hit the court next season in January.

Rusedski revealed he thinks Murray "can do the same" as what Nadal and Federer did.

Rusedski has also acknowledged that Murray has to be extremely cautious about his future decisions, as he turned 30 this past spring. Taking care of his body and scheduling will be a key to achieving more success.

"Andy has got to be smart, the older you get the smarter you have to become," Rusedski added.