User blog comment:Crimson and Darkness/Volume 25 discussion blog/@comment-2602:306:CD9A:C860:C1FD:DC65:EA11:D29C-20180506014209

According to some spoilers I came across. Indra states that Rias has become strong without Issei and that since Issei relies too much on Ravel. That is the gap between his team and Rias team. Not sure what he means by there being a gap.