A standard round robin for 11 teams can be split it into two sets of 5 rounds, plus one extra round. Furthermore, the extra round can be subdivided into two additional matches that can be played on each day as follows:
Day 1
(B K) (C J) (D I) (E H) (F G)
(C A) (D K) (E J) (F I) (G H)
(D B) (E A) (F K) (G J) (H I)
(E C) (F B) (G A) (H K) (I J)
(F D) (G C) (H B) (I A) (J K)
(A D) (B C)
Day 2
(G E) (H D) (I C) (J B) (K A)
(H F) (I E) (J D) (K C) (A B)
(J H) (K G) (A F) (B E) (C D)
(K I) (A H) (B G) (C F) (D E)
(A J) (B I) (C H) (D G) (E F)
(I G) (J F)
Which leaves one unplayed match (E K), so these two teams will be the ones who only wrestle 9 matches over the two day period. This can't be improved upon since if you could play 28 matches in one day, rather than the 27 above, then at least one team would have to play 6 times violating your restriction, since 2*28=56 and 56>(5*11).
Hope that helps.
