McDermott hinted he was keen on bringing Nottingham Forest forward Blackstock to Elland Road having been linked with a loan move for the 27-year-old.
"We're always trying to improve the squad," McDermott told the club's official website.
"I've known Dexter Blackstock since he was a young boy as he was brought up in Oxford and played for Southampton.
"I know him well, he's a good lad and is good in the dressing room. He also has a decent goals ratio.
"Whatever the result was at the weekend (4-0 win over Birmingham) I think it is still important to strengthen and improve the squad.
"If we feel that is the right thing to do then we have to do that if we have the opportunity."
Blackstock signed a new four-and-a-half-year deal with Forest last season when he was a regular starter - scoring seven goals in 39 appearances - but has featured only twice this time round.
Former Hearts skipper Zaliukas played for Leeds' development squad on Tuesday and is understood to be discussing a possible deal with the club in the next 24 hours.
The Lithuania international, a free agent following his release from Hearts, has reportedly turned down recent offers from Rangers and QPR.