West Brom have agreed a fee of £8m for Hull City defender James Chester, according to Sky sources.
Crewe have signed free agent goalkeeper Dave Richards on a one-year deal, with an option for a further year.
Defenders Titus Bramble and Matt Kilgallon are in the final months of their current agreements, and Bramble has consistently said he would like to stay.
The centre-half is back in favour and has started 10 games in succession, but with Sunderland in a fight for Premier League survival his future will remain unclear until the summer.
O'Neill told the Sunderland Echo: "Now, at this minute, the most important issue is trying to get points on the board. I know it's a cliche, but those things can wait."
Sunderland have taken just two points from a possible 18 and go into this weekend's game against Norwich just six points above the bottom three.
O'Neill's side face a daunting run of fixtures post-Norwich as they take on Manchester United, Chelsea and Everton either side of a derby at Newcastle.