There was a time not so long ago when Everton's left back was their primary creative force. Indeed in 2012-13 and 2014-15 Leighton Baines led the team in key passes per 90, and was not far off in 2013-14.
For better or for worse that changed this season. Baines was in and out of the lineup--first due to injury and then due to indifferent form--and ended up playing about 43% of league minutes (he'd averaged almost double that the previous two seasons). When on the field his attacking numbers weren't bad, but they no longer stand out from his teammates to such a degree. Early on in the campaign it became clear that the left side was no longer going to be Everton's reliable source of attacking thrust. Overall this made for an okay but not outstanding season from an individual perspective.
What he did well
While Baines was not the dynamic attacking force of previous seasons, he was still productive going forward and registered 1.34 key passes per 90 minutes, bettered at his position only by Alberto Moreno, Aleksandar Kolarov, and Christian Fuchs. Additionally, only Kolarov completed more crosses per 90 minutes from the fullback position. His pass percentage was a respectable 82%.
Granted they came from a limited number of minutes, the numbers suggest that Baines has remained a useful player in possession and continues to have an eye for creation with the ball at his feet. The glory days of marauding down the left with Steven Pienaar are long gone, but Leighton hasn't lost his attacking instincts by any means.
What he could have done better
The below radar charts plot Baines's performances across a variety of metrics over the last three seasons. The idea for these is taken from Ted Knutson, who explains them well here, and whose charts are prettier and probably slightly more accurate than mine. The concentric polygons represent percentiles based on the rest of the league. Basically, the closer to the outer rim, the higher percentile the player achieved in that stat.
All that being said, the idea here is to visualize some larger trends. Specifically with Baines, it's that his offensive production has remained at a high standard while his defensive production has slowly dropped off.
Note the gradual disappearance of the upper left quadrant--that's Baines's tackles going down, his fouls going up, and a decrease in his ability to prevent opponents from dribbling past him. These symptoms are what you might expect of an ageing player--as Baines slows down, he can no longer be expected to contribute to both phases of play at a high level.
The summer ahead
Baines was left out of Roy Hodgson's England squad for this summer's European Championships and so will hopefully be enjoying a bit of a holiday. With a contract signed through 2019 and no transfer rumors floating about, it seems likely that Baines will be back with the team next year.
The question is what exactly his place will be. He's ranged from merely good to exceptional for several years now, but on the wrong side of 30 one wonders how long he should be considered the first-choice left back.
The answer will have a lot to do with the new manager and the system he installs. Bainesy likely still has another year or two in him, but he needs more help structurally on the defensive side of the ball. He could also thrive as a wingback, and some have suggested a Philip Lahm-esque switch to central midfield, but without a decent amount of minutes watching him it's difficult to say how effective that could actually be.
Final Grade: C
Ultimately I think Baines's season was...okay. Missing four months through injury was a tough start, and while he still posted decent attacking numbers when he played, the tape and the defensive stats paint a picture of a player no longer at his peak.
To be clear, even a non-peak Leighton Baines is still a very good left back, but Everton transitioned this year from a team that relied on Baines in attack to one that didn't. And maybe that's okay--do you want your left back to be running the show going forward? In any case, whether it be Bryan Oviedo, Luke Garbutt, or someone on the transfer market, one hopes that the powers that be have a long-term replacement plan in mind.