If we lose to Chelsea then we wouldn't be drawing one and winning the other 3, would we?
Chelsea won't beat us on goal difference. If they beat us they'll almost certainly finish ahead of us because their other 3 games are piss-take easy. If we win then it's a 5 point gap and we're not losing one and drawing one of the last 3 games. If we draw then then we'd have to win two and draw one for them to finish on equal points after winning their other 3 games. GD is currently 9, plus one for goals scored. 2 more wins for us makes that a minimum 12 GD advantage for them to make up in 3 games: that's 3 4-0 wins. That's not very likely.