"We issued a plea for information to those fans who may have been involved in these incidents", said a statement on Chelsea's website issued on Friday.
Long has had a quiet season by his standards, but did bag his second goal this term in the last clash and often proves his worth when needed most.
Willian, with six goals this season, is always a threat for the Blues.
As a measure of how poorly focused they are, following last week's match, Chelsea have now won only one of their last four Premier League games in which they've scored first.
"If we don't qualify for the Champions League, it means we have to divide the fault, also with the players". They come into this game after three consecutive away defeats.
The two North London clubs will have to convince Chelsea to sell him to a domestic Premier League rival rather than sell him overseas. But, I'm biased and want every great Leicester player back so I through this one to the readers.
But the Italian, expected to leave at the end of the season whether or not his side win the Cup, admitted: "It's hard to explain the reasons why we're struggling in this way this season".
"When you go into games, you know there's certain things players individually and collectively need to understand".
Antonio Conte is not bothered about claims Napoli coach Maurizio Sarri has been approached with a view to replacing him at Chelsea. And when I talk about a lot of mistakes, I involve me, my staff, the players and the club.
Those stats aren't very encouraging for the home side but Southampton looked a much improved unit last week and Hughes may just have kickstarted a rally strong enough to see them avoid the drop. Mark Hughes will be without the services of Jack Stephens as he serves his suspension. With the addition of Ross Barkley during the January window, it's hard to see how the former Leicester midfielder will get a run in the side.