The former West Ham and Blackburn Rovers defender is set to join Turkish side Galatasaray on Sunday after agreeing a deal believed to be worth around £750,000.
Moyes has been linked with a move for Arsenal centre-back Phillipe Senderos to fill the void, but the Scot would not be drawn on transfer speculation although he admitted that, with several members of the Everton backline still on the road to recovery, Neill's imminent departure may create some problems.
Turkish delight: Neill is set to join Galatasaray on Sunday
'I wouldn't be optimistic about replacing anybody because I think it's a difficult market,' Moyes said.
'I certainly won't talk about players at other clubs because that'snot the right thing to do, but I wouldn't be confident that we would beable to get a replacement in.
'It could leave us a gap, certainly in the short term. Joseph Yobocould be back in a couple of weeks time and Phil Jagielka's not too faraway on the horizon, but maybe in the short term it may leave meshort.
Replacement? Out of favour Arsenal defender Senderos
'But over the piece, I think if I get over the next couple of weeks then I think I would be okay.'
Neill has played 15 times during an injury-blighted campaign for theToffees since arriving at Goodison Park as a free agent in September.
The Australia defender is still available for selection fortomorrow's Barclays Premier League fixture against Manchester City andMoyes confirmed that the 31-year-old could feature.
'Lucas will be here tomorrow and will possibly play, so his deal'snot completely finalised, albeit we have agreed terms and Lucas hasagreed terms.
'It was an opportunity for the lad that came about - I think he was very surprised about it and we were surprised also.
'We only heard about in on Sunday, so from that point of view it moved on very quickly.
'But I think with the chance for the lad to get a contract for acouple of years, we had to give him the opportunity to see if he wantedit or not. He's done great for us and I'll be sad if he leaves, buthe'll go with my best wishes.'
Moyes added: 'Everton have promoted Lucas. He got in the team here,played and shown his worth and we always knew he was a good player.
'He'd been out of business for a while in the summertime and intothe start of the new season. But I think for both parties, hopefully itall worked well.'
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