Chelsea's hopes of claiming the Premier League title were severely dented as a late penalty from Fabio Borini, the striker on loan at Sunderland from leaders Liverpool, secured a famous win for Gus Poyet's relegation-threatened side.
Prior to Sunderland's victory, Chelsea boss Jose Mourinho had never suffered defeat in a league game at Stamford Bridge.
After the game, Matic was at pains to point out that he and his team-mates had not taken Sunderland lightly, with a UEFA Champions League semi-final against Atletico Madrid looming large on the horizon.
"We are always focused. For us, the next game is the most important," the midfielder told Chelsea's official website.
"Sunderland was the most important game, we spoke about that before it.
"This is football and sometimes you have to lose. We did give our best but we were unlucky and we lost because of that."
Having returned to Chelsea from Benfica in January, Matic is ineligible for the two-legged tie with Atletico.
Chelsea face Diego Simeone's Liga leaders in Madrid on Tuesday, with the return fixture taking place eight days later.
"Now we adjust the team's focus for the next game, which is Atletico Madrid," Matic added.
"'I'm not going to play, but of course it's going to be a difficult game because Atletico are a good team. But we are Chelsea and the players will be prepared for that.
"We have to do our best to get a good result and to go to the final."
