The four players missed the win over Reading last weekend after testing positive for Covid-19.
It had been expected that only two of the four defenders would potentially be available for tonight’s trip to Oakwell.
But speaking at his pre-match press conference, Ismael confirmed all four were able to end their isolation and train on Thursday.
“I have been told from the medical side that the players are allowed to train from today (Thursday), this afternoon,” Ismael said.
“I will go from there. I need to assess the situation but they will be available for the game.”
Ismael will assess the condition those players are in after they were forced to have a prolonged break from training.
But one player who will be back tomorrow is Grady Diangana. The forward missed the game against the Royals through illness.
One forward who is out tonight, though, is Matt Phillips who hasn’t yet shaken off a muscle problem.
“Grady has been back in training since Monday,” the boss said. “Grady was ill, when you have symptoms it’s not always coronavirus. He had a cold and now he’s back in training. So he is fine.
“Matt Phillips will take a little bit longer. I hope he can be back in the squad in a week’s time. He could be available for Derby or the Preston game.”
Ismael returns to Oakwell tomorrow having enjoyed a hugely successful spell in charge of the Tykes last season.
He joined in October with the club sitting in the relegation zone.
And he went on to drag them into the top six – where they were eventually beaten by Swansea in the play-offs.
That success, though, came during lockdown at a time when fans weren’t allowed inside stadiums.
And the Frenchman admits it’s going to be strange for him being in the opposition dugout at Oakwell with supporters in attendance.
“I was only there for one season and I arrived late – in October,” Ismael said when asked about his connection with Barnsley.
“It’s a strange one because it was the lockdown situation so I didn’t really play in front of a full crowd – it was only the last game of the season, in the play-offs against Swansea.
“So this will be the first time I have played in front of a full crowd.
“But for sure with the players, the connection we had and the connection I had with the people who work at the club – it will be good to see them.
“It was a breakthrough, I am grateful to them. I got the chance to come into English football and manage a team and I think it was a successful story, for sure.
“It shows when everyone is on the same page anything is possible.
“I think it was a win-win situation for everyone.”