Although the information is dated (2002), it is still a very interesting read.
"Other sires listed in Simulcast Weekly whose offspring win over 20 percent of their starts include Avenue of Flags, Boundary, Capote, Carson City, Cee's Tizzy, Danzig, Dehere, Kingmambo, Lord at War, Memo, Not for Love, Nureyev, Quiet American, Unbridled's Song, and Valid Wager."
"Conversely, offspring of El Gran Senor and Silver Hawk were putrid in the mud - although they had very few starters. El Gran Senor's runners won 4 percent of their mud starts, and Silver Hawk did not sire a North American mud winner over the last three years (0 for 44)."
"Other sires listed in Simulcast Weekly whose offspring win over 20 percent of their starts include Avenue of Flags, Boundary, Capote, Carson City, Cee's Tizzy, Danzig, Dehere, Kingmambo, Lord at War, Memo, Not for Love, Nureyev, Quiet American, Unbridled's Song, and Valid Wager."
"Conversely, offspring of El Gran Senor and Silver Hawk were putrid in the mud - although they had very few starters. El Gran Senor's runners won 4 percent of their mud starts, and Silver Hawk did not sire a North American mud winner over the last three years (0 for 44)."