Star cornerback Terrion Arnold sounded the alarms within the Detroit Lions organization on Thursday after he left practice with an issue. The NFC North franchise is one week away from playing the first game of the 2025 preseason, and bad news has already started coming.NFL insider Jordan Schultz reported on X that the 22-year-old defender suffered a strained calf, which forced him to exit the field. Additionally, linebacker Derrick Barnes also left the field."Sources: #Lions CB Terrion Arnold left practice today with a strained calf. I’m told the team plans to be cautious before putting him back on the field. LB Derrick Barnes, who also left practice, should be fine," Schultz wrote.The Lions are coming off a season in which they had to deal with significant injuries, especially on the defensive end of the ball. During the 2024 campaign, 22 players were included at least once on the injured reserve.Big names such as Alex Anzalone, Tre'Quan Smith, Marcus Davenport and Aidan Hutchinson missed several weeks and even the whole season due to injuries. This isn't the most desired start to training camp for Dan Campbell's team, but they still have time to manage Arnold's injury scare and see if he can be fit for the preseason.Thursday has been a busy day in the NFL regarding injuries. New York Jets' new quarterback Justin Fields was carted off the field with a toe injury, sounding the alarms for a team with renewed expectations in the AFC.Terrion Arnold would play his second season in 2025 after playing 16 games in 2024. He recorded 60 tackles and one fumble recovery during his rookie campaign.Terrion Arnold has a high ceiling in the NFLDespite being young and on the verge of playing his second NFL season, Terrion Arnold has shown flashes of his talent. He still has room for improvement in several aspects of his game and offers better coverage on opposing players. Even though he posted 60 tackles last season, he earned a 50.4 pass coverage grade and a 51.5 overall grade from PFF.Arnold is a valuable asset for the Lions, who can't afford to lose him this early in the season. He's just in the middle of his development process, and being out for an extended period would halt his progress.Fans should have more updates on Arnold's health on Friday morning.