Anderson leads the H2H over Nishikori 2-1, and a win would put him as the front runner in the group. At 13/10 he looks by far the greater value of the two.
Meanwhile Federer needs to get himself back into contention, expect a better performance than on Sunday night.
Kevin Anderson to beat Kei Nishikori at 13/10 (Boylesports)
Roger Federer to win 2-0 (vs Thiem) at 24/23 (Marathon)