James (Jim) Lawrence O'Brien was born on 2 August 1896, in Stillwater, Grey, on the West Coast of the South Island of New Zealand.

O'Brien was part of the 11th Reinforcements in J Company as a Private but was later promoted to Sergeant serving in the Auckland Infantry Regiment in the 2nd battalion.

[4] He did not play in their opening game on 8 May but made his first appearance in an official competition match a week later against Marist Old Boys at Victoria Park.

It was then reported that he was being "reinstated as a member of the North Shore club" implying that he had played there initially after returning from the war, most likely in a junior side.

Teams were typically listed in the Friday edition of the Auckland newspapers in their approximate playing order with the first thirteen named being the starting side.

He was named in a match report as playing a "great game" along with Alf Scott, Harry Douglas, Neville St George, and Wheeler.

Early in the match when Australian boxer Mike Flynn had made a break "Somers and O'Brien further improved, and Johnson joining issue the last mentioned swept over to open the visitors' score".

Early in the second half with Auckland trailing 7–8 "Thomas and O'Brien made an attack but lost the ball when within an ace of scoring".

The backs drew most of the criticism and Douglas, O'Brien, and Alf Scott were mentioned as being the "only ones to display their best form" in the losing side.

[45] Devonport continued their good run of form and after a loss to Ponsonby in round 10 they won against Ellerslie, Newton, and Mangere United with O'Brien involved in a try to Tommy Taylor in the later match which was played on Victoria Park.

In Devonport's opening round win over Richmond on 18 April by 29 points to 9, O'Brien passed to Allan Seagar who scored.

[52] Then in their following match, another loss, this time to Athletic 8–6, "O'Brien and Veart played a hard ruck game, keeping the ball at their feet".

[55] Tom Haddon and Horace Dixon had been involved in the lead up toeing the ball ahead before Stan Webb had picked it up and handed it off to O'Brien "who raced over to score".

[61] O'Brien's form saw him chosen in an Auckland trial match in the B team along with Wally Somers and hooker and John Stormont at prop just 16 days after the death of his brother Bill.

[73] The New Zealand Truth newspaper said that "O'Brien, with dribbling rushes, was prominent amongst the forwards, and on one occasion he had a run of nearly 50 yards, being only stopped by Gregory, the All Black full-back".

[75] The Herald had also noted that "a feature of the game was the excellent display given by the Devonport forward, O'Brien, who was a great worker and must have impressed the New Zealand selectors".

The try came late in the match after a "cross-kick by [Maurice] Wetherill was badly missed by [Bill] Spencer, and O'Brien following up gathered in the ball to score".

[82] He was mentioned in both main newspapers match reports but they did not distinguish between the two of them so it is difficult to know who was featuring though much of it was in good open attacking play.

[86] In their opening match of the season on 24 April against Ponsonby they had several injuries and were only left with three forwards, namely O'Brien, Neville St George, and Horace Dixon.

[89] In round 8 he scored in a loss to Ponsonby (19–16) after Cleaver kicked high and the ball struck the goal posts and rebounded into O'Brien's hands.

After the match, and an A/B trial played as curtain raiser, the New Zealand selectors chose the touring side for England with O'Brien missing selection.

His second came after the crowd were allegedly shouting "change jerseys" with the Auckland side leading 42–24 and "O'Brien thought he would get a try, so he went over, and St George placed a goal".

[116] A photograph of O'Brien being tackled by John Stormont was published in the New Zealand Herald after the Roope Rooster semi-final win over Marist 28–11.

[119] He also initiated a try earlier after he "made an opening for List, whose straight running carried him to the visitors 25, where he passed to Seagar, who cut in nicely and scored".

Early in the game he "sent a long pass to List, and the Kingsland centre, racing on a diagonal line, got across with a couple of black backs hanging on to him".

[135] In an article on the representative sides for the season the Auckland Star suggested that O'Brien, Bert Avery, Alan Clarke, Lou Hutt, and J. Payne were the best prospects for the loose forward positions.

His alleged misdeed was not in sight-seeing range of the press bench, and the first indication of something untoward was the Shore forward trekking for the sideline, holding uplifted hands as a token of injured innocence".

Devonport won 18–8 with O'Brien grafting hard along with Sid Rule and Neville St George, and he and Ruby "were outstanding in the loose".

[156][157] O'Brien was then named in the Auckland team to play Buller but he informed the selectors that he was unavailable and Trevor Hall replaced him in the side.

The first came when he fielded a wild clearing kick from Letton "and, being unmarked, went across for an easy try" with Len Scott converting to give Devonport a 10–0 lead.