Thomas Tuchel was delighted to see Chelsea come from behind to defeat Aston Villa 3-1 but was left concerned by injuries to N'Golo Kante and Thiago Silva on Sunday.
Chelsea fell a goal behind when Reece James inadvertently flicked Matthew Targett's first-half cross past Edouard Mendy, but Jorginho soon levelled things up from the spot following Matthew Cash's foul on Callum Hudson-Odoi.
Tuchel introduced Romelu Lukaku at half-time and the Belgium forward flicked the visitors ahead with his ninth goal in 10 Premier League appearances against Villa; he has not scored more against any other opponent in the top five European leagues.
Jorginho again converted from 12 yards to seal victory with his 10th top-flight penalty in 2021. Since Tuchel's first game in charge, the Blues have scored more penalties than any other Premier League side, while the Italy midfielder has scored more spot-kicks than any other club besides Chelsea in that period.
Chelsea's win moved them within six points of leaders Manchester City and level on points with Liverpool, who have a game in hand, but Tuchel was left frustrated by the game going ahead as injuries and COVID-19 infections impacted upon his plans.
Tuchel told BBC Sport: "We showed a very good reaction after their goal. The own goal made things super complicated. The reaction was very good. We defended strong and did not allow big chances. It was a deserved win but hard work.
"We have concerns for injured players. We let Callum Hudson-Odoi play 90 minutes after COVID. Thiago Silva got injured. N'Golo Kante is injured. Mateo Kovacic is playing after injury and COVID without any preparation and training.
"We're just filling holes where we can fill them. We play teams without international duties. Five changes were invented because of COVID.
"Now we're in the middle of COVID and some teams are having games postponed and others aren't. Three changes are a big disadvantage."
Manchester United interim manager Ralf Rangnick insisted five substitutes should be reintroduced in England's top flight for the benefit of player welfare, and Tuchel echoed his compatriot's thoughts.
Asked whether five substitutes should be reintroduced, Tuchel responded: "Of course. We are the only league that play in winter, which I love, but we're not protecting the players.
"All other leagues have five changes. Then we compete against them in the Champions League. It's a bit frustrating. It will not stop.
"Brighton and Hove Albion will play a super physical game then we have two games against Tottenham, who are out of Europe and fully focused on the league and EFL Cup."
Lukaku – who scored in the reverse fixture this season – has a fantastic record against Villa but Tuchel revealed he had no idea about his striker's tendency to score past the Villans.
"No, I was not aware of [Lukaku's excellent] record against Villa," he continued. "I should have known this before. We decided at half-time to have a bit more threat and create more problems.
"I was happy he was involved. He was the game-changer today. We took a lot of risks – 45 minutes was more than the medical department recommended. Who knows if it's the right thing to do?"
