Leinster could welcome back Ireland full-back Rob Kearney and more for this weekend's Champions Cup clash with Bath.
Kearney – along with Luke Fitzgerald, Ben Te'o and Isa Nacewa – all missed last week's disastrous loss to Wasps at home.
"Rob, Luke and Ben, the three of them are getting very close, Isa as well," said Cullen at Leinster's media conference on Thursday.
"A few of them trained today, which is encouraging, so they're getting close.
"We'll get the report on how some of them have trained today and how they've come through. The four of those guys, they've trained pretty well, so the majority of them are in consideration."
The news was less positve however regarding three players who suffered concussion against Wasps – Mike McCarthy, Richardt Strauss and Seán O'Brien.
"The guys with the head knocks, it's looking pretty tight for those guys. It would be unlikely the three of them will feature," added Cullen.
"They're three very different sort of cases: Richardt, Mike McCarthy, Sean O'Brien. Even though the three of them are ok, I think we're always erring on the side of caution with those."