"He has been fantastic. I took him to Tottenham last year from Blackburn. He's one of the best pros I've ever met in my life, a fantastic player, a great trainer.
"He is a massive part of your team. To lose him would be a massive blow for us."
Nelsen has six months remaining of a one-year deal at QPR but Redknapp said: "I'll have to speak to the owner to see what the situation is with that. We'll try (to keep him) but it is difficult."
Last week DC United coach Ben Olsen told American media that the reports were "100 per cent not true".
That slightly contradicts earlier statements from Olsen, who apparently told a fans' question and answer session last year that the club had previously been interested in Nelsen but struggled to match the wages on offer in the Premier League.
Toronto FC has also been mooted as a possible destination for the All Whites skipper.
The 35-year-old has a close association with Kevin Payne, the recently appointed CEO at the Canadian club. Payne was in charge at DC United during Nelsen's spell there, which included an MLS title in 2004, and is an unabashed Nelsen fan.
Former Ipswich town and England striker Paul Mariner is head coach at Toronto FC after previously being in charge of football operations. Mariner is said to be under some pressure at Toronto, after the club went winless in its last 14 games of the 2012 season and finished bottom of the Eastern conference (DC United finished second).
Nelsen would, the theory goes, step into the assistant coach role but have a faster route to the top at Toronto than at DC United.
Nelsen's return to America has long been mooted. He was said to be on the verge of signing for DC United last January, before a last-minute offer from Spurs was presented to his agent. He was also said to be close to a US move at the end of last season before former QPR manager Mark Hughes took him to Loftus Road.
"I loved my time in America," Nelsen told the Herald on Sunday last year. "I met my wife and still have plenty of friends there and it set me up for my career. It's a way better league than it was when I was last there and I would love to go back there one day."
If Nelsen was to move to the MLS, he would have to take a significant pay cut. The American league has a salary cap of US$3 million ($3.6 million) and DC United's highest paid player earns US$650,000 ($781,000). Nelsen is believed to earn around $100,000 a week at QPR.
Though there may be other factors, the timing would be unusual. Any club would have to pay a transfer fee to land Nelsen now, whereas he would be a free agent at the end of the season.
- nzherald.co.nz/Herald on Sunday
