The Spanish fullback has been rightly criticised for poor performances this season, but it was another error by compatriot David de Gea which gifted him a close-range opportunity after fumbling Antonio Rudiger's powerful strike from distance.
De Gea has been under-fire for poor goalkeeping displays of late, which continued against the Blues on this occasion. However, it was creative midfielder Juan Mata, on his 31st birthday, who broke the deadlock after 11 minutes.
Neither side created many clear-cut opportunities after the break. Willian came close at one end while Pedro's goalline clearance in stoppage-time meant Chelsea held firm for an important point - which sees them remain fourth with a two-point gap over Arsenal (5th) and three ahead of Manchester United (6th). Without further ado, here's a look at five hits and flops from an intriguing 1-1 draw:
#5 Flop: David de Gea
Given his poor form of late, it was rather surprising that Chelsea didn't opt to test his nerves in the early exchanges with some speculative efforts. When they did, they snatched a dramatic equaliser before half-time.
Rudiger's powerful strike from 35 yards out saw the Spaniard fumble, rather than comfortably smother the shot and Alonso duly slid across to convert a rebound into the bottom corner.
It happened so fast that naturally replays and slowed footage makes his error appear more damning, but he didn't have much protection from his defenders either as they reacted too slow to help after the shot was taken.
That is his third error leading to a goal conceded in United's last four games (all comps), which is as many as they suffered in his previous 123 matches combined. He was called into action and made an important last-gasp save, denying Higuain after Pedro's excellent pass into his path - otherwise, he'd have featured higher on the list here.