The former Swansea City playmaker is confident that the Uruguay international will go from strength to strength this season after scoring a hat-trick in the Reds' 5-2 win over Norwich City on Saturday.
"It's a privilege to be able to play alongside Luis," said Allen. "I'm just grateful he's on my team. When you're out there playing alongside him, you just have to be in awe of a performance like that.
"The goals, some of the things he did, not many people in world football can do them. He's got everything you need to be a top class."