Despite the 33-year-old goalkeeper being the national team's number one, Arsenal's Wojciech Szczesny started Tuesday's 2-0 World Cup qualifying defeat against England at Wembley.
It was an omission Poland physio Jacek Jaroszewski claimed was due to a hamstring injury picked up against Ukraine and Boruc posted a photo of what appeared to be himself with his right leg in a protective support.
Pochettino, though, claims there is no problem with the former Celtic keeper and expects him to be fit for Saturday's trip to Manchester United.
"Artur is okay," the Saints boss said. "There is some news that has come out, which is not true, regarding his fitness. He is fine.
"He has been training for three days. Today he has been training well and tomorrow we hope he will be training well and that he will be perfect for Saturday's game."
Pochettino also downplayed concerns over Luke Shaw's fitness after the teenage left-back missed England Under-21s duty through illness.
"The last few days he has been training well, he has been okay," the Argentinian said.
"We hope that he will be physically fit for the game on Saturday against Manchester United.
"The rest of the squad arrived back from the international break. The only one that has not arrived yet is Gaston Ramirez and we think he will arrive tonight."
Ramirez has spent the international break with the Uruguay national team - a seemingly welcome break after reports the attacking midfielder is unhappy at Southampton.
The player's agent, Pablo Betancourt, was reported in Italy to have claimed Ramirez really likes the chairman, Nicola Cortese, but not Pochettino.
"I don't really have an opinion on what is in the press regarding those matters," the Argentinian said in response.
"I really don't have a comment on that. I only make decisions based on sports factors, on the performance of the team, for the good of the team.
"I have no preference for any of the 24 players I have available to me. I just make decisions on sports factors."
Ramirez was signed to much fanfare last year, with Saints paying Bologna what was at the time a club record fee of £12million.
Borussia Dortmund, Atletico Madrid and Napoli have all recently been linked to the 22-year-old, who was not in the squad for Southampton's 2-0 defeat of Swansea before the international break.
"I don't want to speak publicly about individual players," Pochettino said of Ramirez's absence. "I don't think that's fair.
"I just make decisions on what is the best thing for the club, the team. I just make decisions based on training and sports factors.
"I try to make the best decisions for my team to win games, to play in a good manner.
"It is always clear that there are 11 starting players, seven on the bench and there is five or six players that have to be left out, so it is a mathematical equation."