With rumors swirling of a training pitch injury for Wayne Rooney late this week, his absence in Saturday's game against Sunderland served as confirmation. Interim manager Ryan Giggs confirmed on Friday that Rooney is dealing with a groin injury. The worry now, as noted here by the Daily Mail, is that the injury could affect Rooney's fitness and even availability for the World Cup.
It should be noted first that Sunderland are fighting relegation and are hardly expected to be competitive against United, with interim manager Ryan Giggs sitting both Rooney and striker Robin Van Persie for the game. Van Persie has missed several games with a knee injury, but has been making progress.
With matches upcoming against Hull and Southampton in the next week, the groin injury is likely to be season ending for Rooney. However, with just a week left in the season and with the big tournament on the horizon, "season ending" may be technically true, but this is hardly a major injury.
A team source tells me that Rooney has a mild (Grade I) strain, but that it is bothersome for him to run and kick. "This is the club being better safe than sorry more than worried about the injury," the source explained. "If Giggs was playing for something like a position or his job, Rooney would be out there."
This type and severity of muscle strain would typically keep a player out up to two weeks, leaving Rooney with limited healing time for United, but plenty of time for England. Technically known as the adductor, the muscle's main function is to move the leg toward the midline of the body. They are key for running, especially lateral motion, and they are involved in the kicking motion as well.
A Grade I strain is the least severe, meaning there was limited damage to the muscle itself, but it can be very painful regardless, depending on where on the muscle the tearing occurred. As well, the muscle becomes more susceptible to further tearing while in it's weakened state. This is why Rooney was removed so quickly from training—to protect him against further damage.
Rooney's injury will require rest more than any therapy. The muscle should be able to heal up in a matter of days if there is no further damage or actions that slow the healing process. The medical staff will be able to use various modalities to assist the healing. Perhaps the best tools are ice and heat, though the location of the injury can often make that uncomfortable, to say the least.
I could not confirm that Roy Hodgson, the England manager for the World Cup, had made any checks on Rooney's fitness. Rooney has dealt with injuries heading into his previous two World Cups, including a broken bone in his foot last time in South Africa. Rooney has been physically limited in both and has made little impression on the pitch.
In the medium and long term, this injury should not be a factor. This type and grade of groin strain tends to heal fully and normally. Watch to see when Rooney is able to come back to training, though again the timing may make it look as if he's off for longer than was necessary.
While some teams have post-season matches scheduled, such as Manchester City, the real tests will come once England start training in late May. England will first go to a training camp in Lisbon ahead of the Champions League final before moving on to Miami for further training and two matches. Rooney should have little issue being ready for these.
Rooney's hard charging and physical style, along with his lower center of gravity have led to a number of injuries, especially to his legs. However, he has come back from all of them positively, showing no real change in his style, speed or skill. There is no reason to believe that this injury will have a different outcome.
The soft schedule that Manchester United have at the end of one of their longest and least successful campaigns helps only England. Resting Rooney ahead of the World Cup is a luxury, but getting Rooney to play at his best is quite the necessity if England are going to go deep into Brazil in 2014's World Cup.