Diego Costa, right, opened the scoring en route to Chelsea's 2-0 win over Hull on Sunday.
Costa very nearly opened the scoring after just nine seconds, volleying just wide of the post, but the game was held up shortly afterward when Cahill and Hull City's Ryan Mason violently clashed heads in the penalty area. The Hull players frantically hurried the medical staff onto the pitch, and while Cahill got up quickly, Mason was on the ground for seven minutes as he was attended to. He was eventually delicately loaded onto a stretcher and taken off, receiving oxygen as the whole crowd applauded.
The remainder of the first half had a slightly odd air. Chelsea was broadly the better side and attacked with some intent, but manager Antonio Conte's levels of exasperation ramped up as the minutes ticked by and his side didn't breach a stout Hull defence. Until the seventh minute of injury time, that is, when Victor Moses dashed down the right, struck a low cross that somehow navigated its way through a thicket of defenders and found Costa, who struck low into the corner. In his 100th appearance for the club, it was his 52nd goal: On balance, you can just about see why Chelsea are keen to keep him.
Hull started the second half brightly, and undoubtedly should have been given a penalty kick in the early stages, when Marcos Alonso hacked at Abel Hernandez's Achilles; everyone seemed to pause in anticipation of the spot kick being given, but the referee remained unmoved.
As the second half progressed, Conte danced farther up and down the touchline, tearing his hair out at the scrappy play of his team, and constantly bellowing instructions that were frequently not carried out. The problem for Hull was that for all their good play and even territorial dominance, their final ball was not good enough to breach a defence that has conceded only 15 times this season.
And that failure cost Hull. With 10 minutes remaining, Chelsea won a free kick on the left and substitute Cesc Fabregas curled it into the area, where some wretched marking opened a broad gap into which Cahill ran and glanced home a header. Costa was substituted shortly afterward, milking the applause from the crowd for all it was worth. He had earned it.
2. Chelsea's frustrations give chasing pack hope
Even as Chelsea led in the second half, there was an air of frustration around Stamford Bridge, their fans rather more anxious than you might expect on a weekend that could hardly have gone better for them. Of the rest of the top six, only Arsenal won, and even then only just. This should have been a day when their supremacy was demonstrated without question.
The surprising dissatisfaction was largely because this was a disjointed performance from Chelsea. Their attack was nowhere near as potent as it had been the past few months, Eden Hazard was anonymous, and only Costa showed much gumption and threat.
Compare this to the previous game between these two sides, the one in which Conte first switched to the 3-4-3 system that has defined this season and started Chelsea's brilliant run. On that day, they were ruthless, slicing through their beleaguered opponents like wire through warm Brie. This time Chelsea were nothing of the sort, and while it would be brave to call any Conte team passive, they were pretty close to that.
The rest of the title contenders could look at this two ways: either a win while playing badly can only be ominous for the rest, or Chelsea are by no means unbeatable or uncatchable. Hull were game but the limitations of their squad were clear, and much like Swansea against Arsenal last weekend, a better side probably would have taken advantage of Chelsea's off day.
At this stage it's tough to see anyone but Chelsea winning the title, but oddly this performance might have given the chasing pack a little something to cling to.
Coming into this game just a point off the foot of the table, away to the side that's five clear at the top, you would forgive Hull manager Marco Silva for not only parking the bus on the edge of their own area but also removing its wheels and disabling the steering.
There was an element of this. Hull's starting formation roughly resembled a 5-4-1, and their collection of vast defenders did form a meaty wall aimed at letting nothing through. Hernandez toiled gamely up front, often with only hints of support from Sam Clucas and Evandro to the left and right.
Yet Silva spent much of the game insisting that his players push up, trying to ensure they did not sit too deep and simply invite pressure. He knew that unless they showed something approaching ambition, they would have little chance of defending for the entire game.
Many managers in this situation, for example, might have objected to Hull centre-half Harry Maguire's frequent jaunts upfield, in which he marauded up the right channel yet allowed many of Chelsea's brighter attacking moments, in the first half at least. But Silva positively encouraged such play from Maguire, even though it could obviously leave a hole at the back to be exploited.
Equally, when Curtis Davies was forced off with injury, Silva replaced Davies with forward Oumar Niasse, moving to a two-man forward line and taking the opportunity to give his side some more attacking punch, rather than defending and hoping to nick a goal on the counterattack.
Hull have a significant task on their hands to get out of trouble this season, but Silva's proactive attitude could well be significant.
Nick Miller is a writer for ESPN FC, covering Premier League and European football. Follow him on Twitter @NickMiller79.
Source: Nick Miller - ESPN