The Gunners signed the Uruguay international in a £26m deal from Serie A side Sampdoria in the summer transfer window.
Torreira earned rave reviews at the World Cup as Uruguay reached the quarter-finals before a 2-0 loss to eventual winners France.
The 22-year-old has been used sparingly in the Premier League so far following his exertions at the major tournament in Russia.
Torreira replaced Matteo Guendouzi at half-time at St James’ Park on Saturday to help Arsenal ease to a 2-1 win over Newcastle United.
Asked about his summer signing’s impact from the bench during his pre-match media conference at St James’ Park, Emery said:
“I want to give every player confidence.
“I am very happy with Matteo and also very happy with Lucas. But maybe in the second half we needed a little more balance on the pitch with the positioning. Lucas gives us this balance.”
Arsenal have won their last two Premier League games thanks to victories over Cardiff City and Newcastle.
The Gunners star came off the bench to help Arsenal ease to a win over the Welsh side before the international break.
The north London side are in seventh place in the Premier League table as Emery looks to lead the Gunners back into the top four for the first time since 2016.
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