The Saints midfielder had to dash off the pitch at St Mary's during the second half of their 0-0 draw with Everton on Monday to answer the call of nature.
The 26-year-old then sheepishly returned in the 70th minute - and got a ribbing from his own fans. Now his team-mates have started teasing him.
Fellow midfielder Morgan Schneiderlin said: "All the players have given him some stick about it - but he said it was better he did it in the changing room than out on the pitch!
"It is the first time I have ever seen that and I am sure not many other players have seen that before.
"But he has taken it well. He loves giving the banter and he has a great personality."