Appearances: 19 starts (+4 as substitute).
Minutes: 1017 in Premier League; 340 in domestic cups; 360 in Champions League.
Statistics (per 90 minutes, Premier League): 83% pass completion, 3.43 tackles won (48.7% successful), 2.02 interceptions.
Rumours linking Baba Rahman to Chelsea started to emerge as soon as last season drew to its close, but didn't actually come to fruition until well after veteran left back Filipe Luís returned to his previous club Atlético Madrid. The long and drawn out negotiations saw Baba arrive only in August, for a transfer fee of £14 million (plus clauses). Baba was expected to reproduce his scintillating form from the previous season, when he was one of the players primarily responsible for Augsburg's surprising fifth place finish in the Bundesliga.
But the highly-coveted and lauded young left back failed to impress either in training, or, when he finally got his chances, in his first few showings in England. Although he provided more support in attack in terms of forward runs and crosses than usual starting left back César Azpilicueta, Baba was left exposed by opposing wingers not only in 1-v-1 situations (his duels against Stoke City's Xherdan Shaqiri certainly come to mind) but also with mistakes in defensive positioning and even on executing clearances.
Despite Branislav Ivanovic's allegedly poor form and Azpilicueta not having a good season either by his previous standards, Baba didn't really manage to mount a challenge to become a starting full back for Chelsea. And it wasn't just because of Mourinho's reticence to play him -- his mistake (and his own reaction to his mistake) against Southampton, which lead to a goal from Shane Long at the end of the first half, drew drastic measures from Hiddink as well. The interim manager opted to start Kenedy instead in the next three matches, who, despite his versatility, isn't actually a full back. Eventually, Baba managed to work his way back into the starting lineup, helped in part by John Terry and Gary Cahill's injuries, and started six of the last eight games of the season.
During this string of starts, especially in the final two games against Liverpool and Leicester City, Baba did (arguably) show signs of becoming a solid player, if not quite a starter just yet. That may not justify the price paid last summer, but it was better than most of what had come before.
The Good: Champions League Round of 16, first leg match against Paris Saint-Germain in Paris. In his biggest challenge of the season, Baba rose to the occasion, keeping Ángel Di Maria at bay and forcing him to change flanks to create chances for his team, while providing good support on the left flank in our few offensive forays.
The Bad: His appearance as a sub in our game against Sunderland at the Stadium of Light, when Sunderland came from behind to confirm Premier League survival. In the chaos and mass confusion following Ivanovic's injury, Baba contributed some of the worst clearances you will ever see from a Premier League player and was also eviscerated 1-v-1 against The Great American Hype DeAndre Yedlin.
The Ugly: The error against Southampton that lead to Shane Long's goal. While Chelsea came back to win, Baba was yanked off at half-time, in part due to his apparent mental breakdown of sorts due to the error. But while his reaction wasn't ideal, and the error was fairly egregious, Hiddink could have certainly handled the episode better as well (see also: Matt Miazga).
Verdict: Outside of a few promising glimpses, it's not been a good season. But Baba still has a lot of potential. The 21-year-old didn't make waves in the Bundesliga by being a bad player after all. He certainly has the physical tools to become a great all-around full back -- he's got good technique, tackling, and crossing ability already -- but in terms of reading the game, consistently making good decisions, and not getting exposed thorough faulty positioning, he's still got a long ways to go.
Only playing time will get Baba to reach higher heights. While it's not readily apparent how and where he will get those chances at Chelsea next season, the club have not been linked with any new left back signings apart from Nathan Aké's potential return from his loan at Watford.
His offensive prowess and the theoretical capacity to develop some defensive skills could make him quite useful to manager Antonio Conte a la Kwadwo Asamoah at Juventus, who played practically anywhere and everywhere on the left flank under Conte's guidance. That possibility alone -- not to mention his age and the four years left on his contract -- could make for a strong case to keep Baba around, even if it's only as depth to Azpilicueta, (and/or) Aké, (and/or) Kenedy.