Rotherham are unlikely to make any more signings before the end of the month, according to manager Steve Evans.
Derby captain Richard Keogh has agreed a new three-year contract with the Sky Bet Championship outfit.
The England U21 defender returned to White Hart Lane last week after completing a season-long loan with Sunderland and was ineligible for Sunday's season finale between the two sides.
Paolo Di Canio has praised the full-back's impact on Wearside, while Liverpool are also reportedly interested, but Villas-Boas remained coy on his plans for the 22-year-old.
"At the moment, Danny goes to the U21 Championship with England and will then return to our squad," Villas-Boas said.
"He has had a great season in Sunderland. We are aware of it. He's a player we have to consider.
"There are decisions to be made at this club in the summer. We have to look to build, but we are also aware that we have to hold on to good players to improve as a club."