LONDON -- Maurizio Sarri backed Alvaro Morata and Olivier Giroud to provide goals for Chelsea and reiterated that defence, not attack, is the area of his team that is concerning him most this season.

Giroud once again failed to find the net as Ruben Loftus-Cheek's first senior hat trick from midfield secured a convincing 3-1 win for Chelsea over BATE Borisov in the Europa League on Thursday.

The Frenchman has yet to score this season and Morata has just two goals in all competitions, and many have suggested that the lack of an elite No. 9 will ultimately prevent Chelsea from challenging for major trophies.

Sarri, however, took encouragement from the two goals in two games that Morata scored prior to the October international break, and Chelsea's head coach is confident that there is more to come from both of his frontmen.

Sarri said: "One month ago we were concerned about the fact the midfielders didn't score. Now in the last three matches, [Ross] Barkley has scored two goals and [Loftus-Cheek] three goals [against BATE]. So I think that if we are able to continue to play this football, maybe in a month the strikers will be able to score.

"You know the characteristics of Giroud. He usually is not used to scoring a lot of goals for the season but he is always very useful for the team. So Giroud is not a problem for us.

"Morata in the last five matches has scored two goals for us I think. But I think they will be able to do better. The most important thing is the team will continue to play this football."

Sarri could not hide his frustration when Chelsea's defence allowed Alexei Rios to bundle in a free kick floated to the back post for BATE in the 79th minute. After the match, the Italian reiterated that the majority of his team's potential for improvement lies in finding greater solidity.

"I think that we could have done better in the last 20 minutes because we needed only to move the ball, to take the positions," he explained. "We conceded spaces to the opponents so in the end we conceded a very stupid goal and I didn't like it.

"I didn't like it because it's very dangerous if you make the same mistakes against a very high level opponent, you are in trouble, like against Liverpool, like against Manchester United. And so we need to control better the match, especially when we are in the advantage.

"Usually the winner [of the league] is the team who concede less goals. In Italy....I don't know here, but I think so. And so we have to improve the defensive phase."

Chelsea's defence is likely to be tested at Turf Moor on Sunday when they take on Burnley, and for Sarri -- who repeatedly lamented the lack of recovery time between Europa League and Premier League commitments -- Sean Dyche's men will present as much a physical challenge as a tactical one.

"We need to change six or seven players for Sunday," he admitted. "It's very difficult in England to play in Europe. I think also in the Champions League, because Liverpool had to play in Naples after two games against Chelsea. United had to play against Juventus, three days after the match here at Stamford Bridge.

"We have to play 65 hours after this match, so it's very difficult for an English team to be competitive also in Europe. I think the match in Burnley will be very difficult because I saw last season a lot of matches of Burnley at home and so I know very well that it is a very difficult match, especially there."