Sri Lanka are 2-1 ahead after successive victories on flat tracks at Headingley and Lord's and will take the five-match series if they can make it three in a row.
Questions were being asked before the series about Cook's suitability for the captaincy role. He was not part of the World Cup squad and seems to have been appointed ODI captain in order to train him for the test captaincy when Andrew Strauss eventually retires, rather than because he was worth his place as a batsman.
Yet he has gone some way to silencing his critics by upping his scoring rate which was 72.47 overall going into the Lord's ODI.
It was not the first time this summer that Cook's scoring speed was under scrutiny on a sunny morning at Lord's. During the second test against Sri Lanka at last month with England heading for a declaration, Cook scored just 26 off 75 balls in two hours as he worked his way towards a hundred.
In the third ODI there he scored 56 off his first 75 balls, tempered by four wickets failing at the other end. He finished with 119 off 143 balls, a strike rate of 83.22.
England's inability to take wickets on good pitches is a talking point and with Steven Finn in the squad, Stuart Broad's place will be debated. He is the only bowler in the attack without a wicket in the series and has conceded 154 runs off 26 overs at 5.92 an over.
He will be back on his home ground, though he has only played one match for Nottinghamshire this season when he took 3-92 against Warwickshire in the county championship in May.
Head to head
P48 Eng 24 SL 24
In England
P18 Eng 9 SL9
At Trent Bridge
Eng P23 W11 L11 Tie 1
SL P4 W1 L3
E vs. SL P1 E1
The average first innings score in ODIs at Nottingham is 244.
In 34 ODIs on the ground, 15 have been won by the side batting first, 18 by the side batting second with one tie. In the eight floodlit matches four have been won by the side batting first and four by the side batting second and the average first innings score is 267.
In the only match between the two sides at Trent Bridge in 2002, England made 293/6 (Alec Stewart 83, Andrew Flintoff 50 in 28 balls) Sri Lanka 249/9 (Romesh Kaluwitharana 52). England won by 44 runs.
Star player, England
Graeme Swann is England's leading wicket-taker in the series, with seven at 13.14. While the critics argue over the merits of the seam attack, there can be no doubt that Swann has made the spinning berth his own in all forms of the game. In 54 ODIs, he has taken 79 wickets at 23.78, conceding 4.47 runs per over.
There can be no quibbling over his batting strike rate either which is a healthy 86.52 overall. In this series he has 18 runs off 26 balls at a rate of 144.44. At Lord's he walked to the wicket in the 50th over, faced four balls and hit a six and a four off the last two balls of the innings off Lasith Malinga, one of the best "death" bowlers in world cricket.
Star player, Sri Lanka
At Lord's rookie No.3 batsman Dinesh Chandimal, 21, became the first Sri Lankan to score two hundreds in his first six ODIs. He was already the youngest Sri Lankan to score a hundred when in his second match against India in Harare he made 111 off 118 balls in June 2010 as a 20-year old.
Sri Lanka have played 31 ODIs since Chandimal's debut, but the retirement of Sanath Jayasuriya should enable the youngster to cement his place in the side.
Captain Tillakaratne Dilshan looked anguished as he watched Angelo Mathews block and turn down runs - he scored one single in 21 balls - to enable the youngster to reach three figures. Chandimal whacked Tim Bresnan for six to go to his hundred, then completed the victory with a four off James Anderson in the next over.
Milestones
Anderson needs six wickets for 200. Only Darren Gough with 234 has more for England.