Some England players may miss out on the British and Irish Lions tour because of poor Six Nations form while there will be more Scots picked than in 2017, says head coach Warren Gatland.
After announcing his coaches for the South Africa tour, Gatland emphasised the importance of 2021 Six Nations performances in his squad selection.
Gatland said the five coaches had put forward over 50 names for selection.
"There are going to be some quality players who miss out," he said.
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Gatland's selection may also be hampered if Premiership Rugby does not agree to release players from English clubs in time for a warm-up Test against Japan at Murrayfield on 26 June - the same day as the league's final.
The New Zealander said there could be "15 or 16 English-based players" considered and "some of them could miss out" when he names his squad in May if they are not released by the league.
Gatland said certain players "have got credit" because of "what they have done in the past", but he stressed that "the Six Nations is the tournament you have got to perform in".
"There are probably some names that would have been inked in a couple of years ago that you are having a serious debate about," he told BBC Sport.
England finished fifth in this year's Championship, winning only two of their games, while Wales won the tournament after narrowly missing out on a Grand Slam in Paris.
But it was Scotland's performances on the road that Gatland highlighted after the side claimed long-awaited victories in England and France.
The Scots' chances are further boosted by the fact that Scotland head coach Gregor Townsend and defence coach Steve Tandy will be touring the home of the world champions with the Lions.
"In this [Six Nations] tournament Scotland had two great wins away from home," Gatland said.
"You have got to be conscious of that because we are playing away from home."
He continued: "There is no doubt that with their form in the last 12 months and particularly at the Six Nations, there will be more Scottish players represented and I think that's good."
Jones 'in contention' for captaincy
The Lions will have a new captain this year following the retirement of two-time skipper Sam Warburton.
England captain Owen Farrell, lock Maro Itoje and Scotland full-back Stuart Hogg are some of the names most frequently discussed, but Wales captain Alun Wyn Jones is the current favourite.
Gatland said Farrell "would probably admit it wasn't his greatest Six Nations" before adding that many Saracens players "have credit for what they have done in the past".
The Lions coach said lock Jones was "definitely one of the guys in contention" for the captaincy.
"Coming from a team that has done reasonably well in the Six Nations and having the respect of others in the squad is probably fairly important," Gatland said.
Lions to have two bases in new schedule
The original tour schedule is currently under review because of the impact of the coronavirus pandemic and Gatland said a new schedule would be confirmed by the end of the week.
He explained that there would still be eight games in total played in South Africa, with three Tests as per usual.
Gatland added that current plans were to have one training base at altitude in Johannesburg and another in Cape Town.
"We might start at altitude, then go down to Cape Town and back up for the last couple of Tests. That is how it looks at the moment. It is not 100% confirmed," he said.
The Lions will play in a coronavirus bubble and Gatland said he preferred having two camps to offer some variety to players.
"Having spoken to the coaches during the Six Nations we know the challenges of being locked up in a bubble," he said.
"For me that's a priority, it is not about the rugby at the moment it is about the welfare of the players and trying to ease some of those challenges of being locked up."
British and Irish Lions 2021 original schedule
26 June - Japan (Murrayfield, Edinburgh)
3 July - DHL Stormers (Cape Town Stadium, Cape Town)
7 July - South Africa Invitational (Nelson Mandela Bay Stadium, Port Elizabeth)
10 July - Cell C Sharks (Jonsson Kings Park, Durban)
14 July - South Africa 'A' Team (Mbombela Stadium, Nelspruit)
17 July - Vodacom Bulls (Loftus Versfeld, Pretoria)
24 July - First Test v Springboks (Soccer City, Johannesburg)
31 July - Second Test v Springboks (Cape Town Stadium, Cape Town)
7 August - Third Test v Springboks (Ellis Park, Johannesburg)