A combination of poor results and not being able to raise a full eleven during that season led to the county's removal from the first-class game, although Sainsbury remained as captain until 1888.

Playing for the school's cricket eleven he acquired a reputation for his slow underarm bowling, which could deceive even the most wary opponent into conceding his wicket.

[5] A few days later he appeared again for the county side, against Clifton, who had the Australian Test cricketer, Billy Midwinter, in their team.

Sainsbury scored 96 not out, including a "resolute" partnership with Stephen Newton, before rain forced the game to be drawn.

[7] In two further appearances for Somerset in 1877, Sainsbury did not surpass the score he reached against Dorset but claimed two further wickets, both against the Gentlemen of Wiltshire.

In doing so, he batted for over four hours,[11] and shared an eighth wicket partnership of 114 with Francis Reed, out of a Somerset total of 249.

[27] The arrival of two professional players, and the acquisition of a permanent home ground in Taunton helped strengthen the club so that in 1882 they were admitted as a first-class county.

[36] He did not reach 50 in his next three appearances for the county, but against Gloucestershire he top-scored for his side in their first innings with 59, and then when Somerset were forced to follow on, he scored his only century in first-class cricket, amassing 116 runs before he became one of W. G. Grace's eleven victims in the match.

[37] Sainsbury played in seven matches during 1883, and achieved his highest batting average in a season, his century and two fifties boosting him to 27.92.

[38] Playing for Lansdown against the touring Gentlemen of Philadelphia the following month, he scored the only century of the match, reaching 108, and sharing a first wicket partnership of 149 with E. M.

[39] He batted poorly for Somerset during 1884, failing to reach double figures in most of his innings, and hitting a top score of 30 for the county.

[34] Following the departure of Somerset captain Stephen Newton, who played all his first-class cricket in London from the 1885 season onwards,[40] Sainsbury was given the club captaincy.

Sainsbury scored 0 and 13 opening the batting for his side, but the bowling of Edward Bastard, who claimed eight wickets in the first innings and three in the second, helped Somerset to a five-wicket victory.

In reply, five of the Somerset batsman were out for ducks; Sainsbury, Parfitt and Albert Clapp were the only ones to reach double figures.

[45] Matches were played more frequently in August, and Sainsbury and his Somerset team had just four days to recover from their defeat before travelling to The Oval to face Surrey.

Following on, Somerset mustered a more respectable total of 251, aided primarily by a century from Octavius Radcliffe and 85 from Hewett.

[46] Morale was low at Somerset, and the county could not raise a full team to face Hampshire at Southampton a week later.

[55] An emergency meeting was held in Taunton, during which a new club secretary was appointed, rules were altered, and wealthy benefactors were sought.

[57] Throughout 1886, Sainsbury's batting continued to be more fruitful than his efforts in the previous two years of first-class cricket, and he regularly made scores in the twenties and thirties.

[58] Toward the end of the 1886 season the arrival of Sammy Woods and George Nichols vastly improved the quality of the bowling for the county, but 1887 was nevertheless marked by a slow start.

In contrast, in a match played for the MCC, Sainsbury struck his highest total for the side, scoring 180 runs against Wiltshire at Lord's.

Sainsbury was unable to be present for the meeting, but had sent a letter advising that if he was removed as captain, he did not feel he could play for the county any more.

His letter was not well received at the meeting, and it was decided to replace him as captain with another player who lived closer to Taunton, and was able to play more of the county matches, as Sainsbury had missed a number during 1888.

[64] At Gloucestershire's annual meeting in April 1891, W. G. Grace welcomed Sainsbury to the club, and there was some mirth at the expense of Somerset regarding his move.

[67] Sainsbury played 13 times for Gloucestershire that season, with his highest score being 36,[34] made against Yorkshire at Bramall Lane, Sheffield.

[34] He continued to play for Lansdown, who he captained in 1893, scoring over 1,000 runs that season,[70] Clifton, and the MCC for a number of years.

[56] In From Sammy to Jimmy: An Official History of Somerset County Cricket Club, Peter Roebuck suggests that Sainsbury was key in the improvements made by the county in 1888,[71] but fellow cricket historian David Foot appears to portray a more negative image in his book Sunshine, Sixes and Cider, suggesting that during Sainsbury's time as captain he may have included players in the team "on the strength of [their] social charm and ability to drink into the early hours".