As for Chelsea vs Sheffield United, Sheffield United is lucky to score one more goal during injury time, Chelsea always have a problem in their back line, just take a look with their previous matches, regardless what the outcome, the opponents can scored a goal.
Manchester united was actually lucky to have been able to draw probably because they were playing from home so it challenged them to want to make sure they win or at least get a draw because it will really feel embarrassing loosing at home, Liverpool seem to have lost their rhythm in early minutes of the second half but later got back from the 70th minutes. Chelsea has been consistent with draws this week i think it's because of the speculations around the possibility of their coach loosing his job so he had to make sure he makes up for all the lost times
Showing slight improvement with their performance is what Chelsea was exhibiting but then it later turned out that i couldn't even really see much of improvement because they just be narrowly escaping with draws which actually isn't really bad but then it should be further improved so they can be able to rank up a little just before the end of the season, i wouldn't say Sheffield was lucky but i would say they actually utilized the opportunity they had well enough.