The differences between the teams were:
Team A:
1 - Tier 5 BB (fail div)
1 - Tier 4 CA (fail div)
1 - Tier 5 DD (fail div)
Team B:
1 - Tier 6 Cruiser
2 - Tier 6 DD
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The substitution is as follows
Tier 6 Cruiser -> Up one "type" and down one "tier" = Tier 5 BB
Tier 6 DD -> Up one "type" and down two "tier" = T4 CA
Tier 6 DD -> Unable to find alternate. Dropped 1 Tier = Tier 5 DD
The "Battle Tier" of the match was Tier 7, so Tier 7s cannot be substituted, but the lower tiers can be altered in the matchmaking queue is long enough. This is talked about in our "How It Works: Matchmaker video around the 7:14 mark.