Robbo MOTM for me; he was the only one defending properly in the 1st half and his desire to win the ball back made the 2nd goal. Matip close 2nd, 3rd could be Fabinho, Thiago (I thought he did do a lot of good things besides the assist, like pressing and tackling), Trent or Alli, but I'll go for Firmino whose introduction changed the game.
Martinelli was unplayable in the 1st half; clearly took Klopp's praise to heart and was trying his best to impress him. Arsenal are getting closer to us; they just missed a bit of sharpness and experience in key moments.