O'Brien, who recently tested positive for Covid-19, is likely to make his return in Tuesday's Championship home game with Preston after three days of individual work under medical protocols.
Intense speculation continues to rage over his future, with Leeds keen to sign the 22-year-old, whose deal expires next summer.
Speaking in his monthly address to supporters on the club's official website, he wrote: "The transfer window is still open, and it is still possible that players can leave and arrive before the end of August.
"There has been a lot of speculation surrounding Lewis O’Brien’s future, in particular, and I can confirm we have received and rejected two transfer offers for him.
"We respect every player’s desire to test themselves at the highest possible level, but equally any transfer must be right for Huddersfield Town, both in terms of value and timing.
"We will do our best to keep supporters informed as the window reaches its conclusion."
Speaking about the situation with O'Brien at his pre-match press conference, Carlos Corberan commented: “I did not talk with him about any (transfer) situation.
“I cannot be thinking now about (speculation) on O’Brien because O’Brien is with us. Now, unfortunately, we don’t have him working with the team because we know he has had Covid.
“I think he is going to be one of the first players to adapt and come back again with the team and to the normal level.
“He had a test (on Wednesday) and finished his isolation process, so we hope he can come back to the team just as fast, as he is an important player for us.”
With due respect to the majority of Town’s other players, replacing O’Brien would represent a hugely difficult task for Corberan and it is something that the head coach, while loath to speak about the midfielder’s future, fully appreciates.
Corberan said: “I know how important he is as a player. I know what O’Brien brings from the physical point of view and on the ball and I know how difficult it is to find one player that does the same as him in every game.
“As every time I look at his GPS values, he is one player that every two days is able to achieve more than 1,500 high-intensity metres – something that is not usual in any player.
“I never had the experience to see these values before in my life.
“I know he is an important player for everything he does on the pitch.
“It is not only running as he gives a lot of meaning to the running.
“One thing is to run and the other is to run with ideas. He has a lot of impact in the team.”