Keaton Jennings could not have made a more satisfying introduction to Test cricket: a century on debut against India in Mumbai. Highly regarded by the England management, and viewed as captaincy material, he was a batsman for the future at a time when the prolific career of his fellow England left-hander, Alastair Cook, was nearing its end. But life proved more taxing for Jennings than had been imagined. But the time Cook retired, he had played 22 Test innings and had added only one more half-century, that also on his debut India tour.

Jennings' career took shape in fine style in 2016 when, at 24, he was named as the County Championship player of the year by the Cricket Writers' Club. It recognised a season in which he had been the leading run-scorer in the competition with 1,548 runs at an average of 64.5 with seven hundreds, including a double century against Yorkshire. His career-best 88 as Durham were beaten finalists in the NatWest Blast was also the highest score during Twenty20 finals day.

England recognition came on the 2016 tour to India, as a replacement for the injured Hasseb Hameed, and he made an immediate impact with a century on debut in Mumbai. Subsequent leadership experience with England Lions, plus the Durham 50-over captaincy, saw him identified as a potential Test captain, but his form plummeted the following summer and after eight innings against South Africa without a half-century, his footwork increasingly static, he was dropped after six Tests. Eager to press his England claims, and concerned about Durham's faltering status on and off the field, he sought salvation with a move to Lancashire.

He topped the averages in his first Lancashire season, and won a recall to the Test side, initially against Pakistan, and then for a home series against India - Cook's last - but often got out after doing the hard work. The freewheeling county strokeplay of 2016 had become a distant memory.

Jennings, a tall left-handed batsman, made his first-class debut for Gauteng against Free State in his native Johannesburg in December 2011 aged 19, having spent a season with Durham, where he made 1,319 runs in Academy and Second XI matches. He is a former South Africa Under-19 captain who led the touring side in England in 2011 and is the son of former South Africa coach Ray Jennings, but committed himself to serving a four-year qualification period to become eligible for England.

His strong north-east links should not be discounted - his mother is from Sunderland - but his arrival at Chester-le-Street owed more to the friendship Durham coach Geoff Cook struck up with his father when they played domestic cricket in South Africa, Cook for Eastern Province, Jennings for Transvaal.

A patient batsman with an old-fashioned willingness to occupy the crease, Jennings enjoyed a prolific 2nd XI season in 2012 and earned his first-class Durham debut against Surrey in August 2012, a week after making 201 for the Seconds against Ireland A. He made a favourable impression with an assured 70 spanning two and a half hours against Lancashire at Aigburth in his third first-class match for the county.

For a while he struggled to progress, his innings often conducted on challenging Riverside surfaces, but relief came in his first full season against Derbyshire at Chester-le-Street in July. He compiled an increasingly careworn 90 in the first innings, but that proved to be a scouting mission for his maiden Championship hundred second time around: a more assured 123 before he was run out. Durham had secured the title by the time he added a second hundred in a more relaxed season's wind-down at Hove.

Just one more Championship hundred followed in the next two seasons, although he did make his List A debut in 2014 against Sri Lanka as Durham gave him opportunities to expand his game in the 50-over format. Their faith was to be well rewarded in 2016 and, even though Durham were relegated as part of a ECB financial bail-out, he decided to remain at the county for at least one more season.

That season proved to be a disaster, a single century and an average of 25.79 falling well below the standards he had set the previous year as he fell down the England pecking order and missed out on an Ashes tour. Lancashire won the battle for his signature.

ESPNcricinfo staff