"0.975 Chelsea 1.5 Watford 0.875.
Yesterday Watford was playing away and the match closed
0.8 Chelsea 1.5/2 Watford 1.05"
I can't see any discrepancy in these odds, the way you described this scenario. The -goals for chelsea increased and their odds decreased, since they are now playing at home, what's the problem with that? You obviously think that the goal difference should have been set higher, but that's just an (informed) opinion. I might be missing something here, i don't think i am, but i might, but these odds seem just right for me. If i were the bookmaker my rationale would be: Chelsea only have to win with one goal difference to qualify and will possibly aim for a couple of goals to safeguard their victory during game time, i don't see any extra incentive here, it's not even a league game, so i can't see any reason for a 2 goal difference, better set it at 1.5/2 and lower the odds for chelsea.