 On 27 December 2013 , Federer announced that Stefan Edberg was joining his team as co @-@ coach with Severin Lüthi . 
 On 27 December 2013 , Federer announced that Stefan Edberg was joining his team as <a href='uninflect' title='1'><mark>co</mark></a> @-@ coach with Severin Lüthi . 
On 27 December 2013 , Federer announced that Stefan Edberg was joining his team as coed @-@ coach with Severin Lüthi .