Daryl Horgan is expected to follow his Dundalk team-mate Andy Boyle to Preston North End.
Boyle (25) had attracted the interest of Scottish Premiership side Rangers, as well as Barnsley, Bolton and Oldham in England.
But the centre-half has agreed in principle to join the Championship club next month.
Winger Horgan (24) was also wanted by Rangers while Sunderland, Newcastle, Aston Villa and Ipswich Town were keen too. However, Horgan is also set to agree terms with the Championship side, and challenge Ireland team-mate Aiden McGeady for a left-wing slot.
Meanwhile, Dundalk are seeking to replace Boyle with St Patrick's Athletic defender Sean Hoare.
Hoare is still under contract at St Pat's and would command a fee should he leave Richmond Park, the Irish U21 defender also attracting interest from Shamrock Rovers and Cork City.