London, Jan 3: Manchester United boss Sir Alex Ferguson has asked his ace striker Cristiano Ronaldo to stop retaliating against his opponents on the field, because the spotlight is always on him.

The Portuguese star has been involved in a number of controversial incidents of late after being fouled.

Ronaldo has kicked out at Scott Brown of the Celtic, the Spurs' Michael Dawson and Stoke's Andy Wilkinson. This week he had a tunnel bust-up with Middlesbrough defender Emanuel Pogatetz, The Sun reported.

Ferguson said: "Of course, I can understand Cristiano's frustration. I can understand it all right. He's produced little moments of displeasure at the treatment he's getting."

"They have been trivial things but because it is Ronaldo, as he points out himself, it is magnified. But that's the penalty for being a great player. He has to understand that," he added.

Ronaldo will be rested for FA Cup tie at Southampton as Ferguson juggles his squad.

Striker Carlos Tevez will also be missing after being given time off to go home to Argentina. His loan deal has still not been made permanent.

And, Ferguson said United chief executive David Gill is having problems agreeing the details with his owner and agent Kia Joorabchian.

He wants the 32million pound that was verbally agreed when he first moved to the club, but United now value Tevez at less.

Ferguson said: "We have been trying but it's difficult sometimes with agents."

Meanwhile, United have completed the permanent signings of Serbs Zoran Tosic and Adem Ljajic from Partizan Belgrade for a combined total of 16 million pound.

Winger Tosic, 21, will join immediately while midfielder Ljajic, 17, will stay at Belgrade for another year. (ANI)