Pochettino taken aback by Chilwell's starts for England after injury
Chilwell last started for Chelsea on March 2 against Brentford and has played just a few minutes for the London club since then, as a late substitute in the FA Cup against Leicester.
Nevertheless, the 27-year-old featured for the whole of England's 2-2 draw with Belgium at Wembley on Tuesday, three days after spending 67 minutes on the field in a defeat by Brazil.
Chelsea currently have nine players ruled out of Saturday's Premier League match with Burnley at Stamford Bridge, with several others to be assessed following international duty, including Chilwell -- who suffered a blow to his knee against Belgium.
"He didn't play after Brentford, then he played only a few minutes against Leicester," said Pochettino. "(Then) he started two games (for England).
"It's a surprise for us. It's bad luck because he got a dead leg in the last moment against Belgium. Now we need to assess if he can be available."
Enzo Fernandez, who played twice for Argentina in the United States during the break, will also have his fitness monitored ahead of this weekend's match.
Chelsea confirmed earlier this week that Romeo Lavia would be out for the rest of the season.
The 20-year-old midfielder who joined Chelsea from Southampton in pre-season for an initial £53 million (62 million euros), has managed just 32 minutes of first-team action this term following ankle and thigh problems.
"It's a difficult situation for him," said Pochettino. "He's sad. He only played 30 minutes, for a new player at the club.
"When we signed him, he arrived with problems. He couldn't train with us for the first months. Then when he was ready he suffered a problem in his feet.
"He recovered, he played 30 minutes then got injured in December. Then he didn't have the possibility to train. It's really sad news."
But leading scorer Cole Palmer could face Burnley, with the 21-year-old having not featured in either of England's recent games.
"I talked with him," said Pochettino. "He's a little bit disappointed because he couldn't play with the national team.
"The first game he had a small problem," the Argentinian added. "He thought maybe he'd play the second game. Now he's OK, is training well. The plan is he will be available for Saturday."
Chelsea are 11th in the table, with Burnley in the relegation zone.