Wales quartet Gareth Davies, Tomas Francis, Cory Hill and Kristian Dacey have been called into the British and Irish Lions squad.
All four players will join the Lions on Saturday, a day after starting in Wales' 24-6 win over Tonga in Auckland.
Lions head coach Warren Gatland said having Hill, Dacey, Davies and Francis already in New Zealand helped their cause, as his team prepare for the opening Test against the All Blacks on June 24.
"We have said all along that we need to give ourselves the best chance of winning the Test series and that could potentially involve calling up players," he said.
"Bringing in these players from an identical time zone, who can hit the ground running and step straight in rather than having to adjust following long-haul travel will help us manage players before the first Test, give us quality training numbers to prepare properly as well as offering us options for selection for the Chiefs match."
The Lions face the Maori All Blacks on Saturday before backing up for a clash against the Chiefs just three days later.
Gatland expects to make further additions to his squad in the coming days.
He said: "These are players currently on international duty who we are looking forward to welcoming into the Tour party as we did with several players in 2013.
"I spoke to all the Home Union coaches prior to departure and explained our thinking and they were all supportive."
Davies, 26, is the most experienced of the Welsh quartet, having played 25 Tests, while Francis has featured 23 times.
Hill and Dacey have made just 10 Test appearances between them.