Manchester United have launched an internal investigation into their debilitating injury at the club this season.
United have suffered continuous injury setbacks this season with under-pressure boss Ten Hag often unable to field his strongest line-up for some matches.
The crisis deepened this week with defenders Martinez and Lindelof ruled out for a month with calf and hamstring injuries respectively, joining Luke Shaw and Tyrell Malacia on the sidelines.
Asked why United were suffering so many injuries, Ten Hag said on Wednesday: 'We have an idea but we will work on that internally and deal with it.'
'There are no more issues, we don't need any!' said Ten Hag. 'In the front line and midfield we are okay and we have options there, but in the back line we have a lack of options.
'The good thing is back that Rapha Varane and Jonny Evans are in training this afternoon. Yesterday Harry Maguire was back in training.'
Ten Hag blamed United's persistent injuries on an 'overload' of games and pointed out that other Premier League teams have suffered as well.
'You can't prevent it, it's not only us who've had this,' he added. 'The standards of the Premier League from an intensity perspective are so high, the overload of the schedule, international football is so huge, and we have internationals in our squad.
'Man City, Liverpool and Newcastle have problems, many other teams. We don't train because we recover then you go up to the next game.'