The roller-coaster ride that has been Aston Villa's season continued at Villa Park on Sunday when Paul Lambert's team, fresh off home wins against Norwich City and Chelsea, were soundly beaten by Stoke City.
After thrashing Norwich and besting the league-leading Blues, Villa squandered an early 1-0 lead and were thoroughly outplayed by Stoke for the majority of their match.
The four goals Stoke put past Brad Guzan bring Villa's shaky defence back into question. Facing a Stoke team that has struggled in away matches, Villa were embarrassed by a host of defensive errors and each member of Villa's back four was partially culpable for the defeat.
Leandro Bacuna, Villa's breakout signing of the season, had his worst day in a Villa shirt by far. The right-back was beaten with regularity by Stoke's Marko Arnautovic, leaving Bacuna partially responsible for three of Stoke's four goals.
Similarly, Nathan Baker suffered a complete nightmare of an afternoon. Baker's failure to clear the danger twice allowed Stoke to score and he was poorly positioned to intervene on another goal.
While not as dire as their team-mates, Ron Vlaar and Ryan Bertrand were also sub-par against Stoke. Both men have been reliable defenders this season and failed to compensate for the poor performance from Bacuna and Baker.
The dismal display by the Villa defence leaves Lambert with great uncertainty going forward. Lambert had seemingly settled upon the foursome as his first-choice defence, but there are now question marks surrounding his choices.
Vlaar, despite playing poorly on Sunday, is still Villa's best defender and should not lose his place. While less proven than Vlaar, Bertrand should continue to start at left-back over the likes of the inconsistent Joe Bennett and the underwhelming Antonio Luna.
Baker is the clearest problem of the four. The young defender has never been consistent in a Villa shirt and still lacks refinement. Lambert's constant selection of Baker shows the manager's confidence in the defender, but there is little evidence from the pitch backing up Lambert's decision.
Ciaran Clark has made way for Baker and should return to the starting XI immediately. While the Irishman has his own shortcomings, he is a more skilled, composed and dependable option than Baker.
The potentially imminent return of Jores Okore from injury offers further incentive to displace Baker from the starting line-up. Okore is a very promising defender and his development, once he returns to fitness, should not be halted by Baker.
Villa's right-back situation is less simple. Bacuna has been one of the best bargain purchases of the season and is Villa's second-leading goalscorer, but his future may not be in that position.
Originally signed as a midfielder, Bacuna has entrenched himself at the right-back position thanks to the poor form of Matthew Lowton. Lowton, whose passing and interceptions made him a mainstay in last year's squad, has defended poorly this season and subsequently lost his place to Bacuna.
However, Bacuna's poor outing against Stoke may force Lambert to reconsider. Bacuna's offensive contributions have helped overshadow his deficiencies, but Arnautovic is hardly the first opposing player to expose the Dutchman's shortcomings as a defender.
Bacuna is athletically impressive, but his reaction time, poorly timed challenges and lack of positional awareness are concerning. Lowton lacks Bacuna's quickness and strength, but he reads the game very well and has more experience as a defender.
Both players are more impressive going forward where they offer different dimensions to the Villa attack. Bacuna makes dangerous runs into the box and has proven himself as a deadly free-kick taker. In contrast, Lowton has better passing vision and crossing ability.
This leaves Lambert to select between similarly flawed players. Lambert has denied rumours of a rift with Lowton, spawned by the lack of action the Englishman has seen in 2014, and he must consider reinstating him if he does not view Bacuna as the club's long-term right-back.