Ruddock led Wales to their first grand slam in 27 years, but left his job last week citing "family reasons", with skills coach Scott Johnson put in temporary charge.
Defensive coach Griffiths maintains the playing squad must remain fully focused on the Six Nations Championship clash with Ireland on February 26.
"Personally I feel it is really disappointing for a great friend and colleague," said Griffiths.
"But professionally the job is still to be done and in the short term I am focused on the next challenge, and that is Ireland at Lansdowne Road."
Griffiths added on BBC Radio Five Live's Sportsweek programme: "It has happened and we all have to move on.
"I am not going to pretend it was not a bit of a dark cloud over proceedings [at training], but as time goes on, the wounds are healing and this week we know it is going to be full-on preparation for the Irish game."