The youngster completed his move to Anfield from Inter in January and found the back of the net on his full debut in the 5-0 rout of Swansea City on Sunday.
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"I'm really happy for him," the Reds star told the club's official website. "We were talking about the pace of the Premier League and even with the training sessions he has found it is much quicker than in Italy.
"He will need time to settle but that goal will give him confidence. We could see a lot of positive things from him against Swansea. Hopefully he will be a great player for now and for the future as he's only 20 but he will need time.
"Every single young player who comes to the Premier League finds it difficult when they first come. It will be the same for him."
Lucas revealed how he had played a part in convincing Coutinho to come to Anfield and how he is now helping him settle in, adding: "I've told him about how he will be successful here. He is trying to adapt and play quick because he knows he needs that tempo to be successful.
"He has the skills and the ability to do well. We just need to support and help him."