The Liverpool defender has established himself as a key member of Brendan Rodger's first-team, but his less than stellar performance in Wales proved he is only 21 after all.
After appearing to have no future at Liverpool following the sacking of Kenny Dalglish John Flanagan has, with the help of Brendan Rodgers, turned his Anfield career around.
In light of Jose Enrique's long-term absence and Glen Johnson's playing time punctuated by poor form and injury, the academy product has not only featured regularly, but excelled at making the most of the opportunity to now be seriously considered a permanent fixture even after their return.
So much so in fact that it is believed Rodgers plans to offer Flanagan a new contract in the summer. Just reward you might say.
While all this is good news it should be remembered that 'Flano', as he has been affectionately called by team-mates, is still only 21. He is far from the finished article and it should put his poor performance against Cardiff into context.
An auxiliary right-back, Flanagan was asked to play at left-back on Saturday and although he has played in this position before it is hardly a natural one for him. Often he would turn infield and pop the ball off with his right foot, reluctant to use his left to go on the outside.
That may have explained why he wasn't at his best. More likely it might be to do with the idea that he will still struggle for consistency in his game in a period where most of his maturing will come from as a footballer.
More is expected of Flanagan now which is a measure of his rapid progress. After producing a terrific performance against Manchester United, it was only natural for fans to anticipate the same when he came up against inferior opposition in Cardiff.
It wasn't to be the case. 'Flani Alves', as some Liverpool fans on Twitter have jokingly labelled him, was not Liverpool's worst player. Far from it. But he was below par.
As Joe Allen struggled to protect him, so Flanagan was badly exposed to Fraizer Campbell, Jordan Mutch and in the second-half, Craig Bellamy, who had switched flanks, running at him.
If there is a clear weakness at present with the three-time England Under-21 international it is his lack of pace and propensity to allow attackers to get goal side of him. He can be rash in the tackle at times too.
With more experience some of these issues will iron themselves out and that is what needs to be remembered when the point comes, as it inevitably will, when Flanagan experiences a true dip in form. Good thing then the boy from Liverpool has time on his side.
Do you agree John Flanagan was poor against Cardiff and is this a sign of a player who is still developing