The players who must prove their worth this season

Mignolet & Reina?
No one seems sure as to whether Rodgers will give Reina a chance to compete for the starting job this season or is just waiting for and/or weighing the best offer for the soon-to-be 32-year-old.  The Spanish International made the trip across the pond as part of the squad for the US tour, but so did Borini.  I think he should be able to stay and fight for the top spot, there's nothing more healthy than a little competition and after last year, Mignolet should know his spot is far from safe.

The 26-year-old Belgian was fifth worst in giving up 50 goals last season and his 93% cross claim percentage was 28th in the league.  The demeanor of Mignolet was what worried me most, he didn't seem too concerned with taking control on defence and a seeming lack of communication between him and his defenders cost us a few goals last year, possibly the league as well.  Personally, if he doesn't show the form that lead us to buy him for £9m from Sunderland last summer, I say start looking for his replacement.

Sakho
The more and more I looked into Sakho's performance last season, the more discouraged I became.  Whenever he was on the pitch, our defence was as fragile as a United fan's confidence, one remote slight and it would collapse.  The biggest piece of the puzzle is what the 24-year-old French centre back did to warrant a -0.52 goals on pitch difference, by far the worst among club regulars.  His statistical output otherwise was good to excellent (92.5% passing success rate), which leaves unquantifiable solutions such as positioning and communication.  No matter what, if he continues the path he is on, which may have been due to game-style adjustment, he shouldn't be in a Liverpool kit by the end of next summer.

Martin Kelly & Glen Johnson
Oh Martin Kelly, too many injuries, too little time, what could have been? And now the clock nears the stroke of your LFC career end.  It's too bad the freshly-turned 24-year-old has not been able to put together a decent amount of appearances since his first team debut in 2009.  He needs a huge season to justify him staying even though his contract is until summer 2017.  I've always thought he had the talent, maybe he simply lacks the physicality to survive English top flight football.

Despite reports of his imminent demise, Glen Johnson did the same things at the same rate he's been doing for the past four years or so.  He set a career high in successful pass percentage at 84.1%, he still posted a 1.11 chance created per 90, and was only dribbled past by 0.82 per 90, his career average is 0.73.  We'll probably never see the kind of season he had when he was 25, but it's a contract season for the soon-to-be 30-year-old, so we should him at his possible best.

Some other players come to mind, but the aforementioned are the most crucial.  If Jose Enrique returns to his form of the previous year and avoids injury, he'll be fine.  Joe Allen will probably stay as long as he wants to be a bit part of a much bigger picture, ditto for Lucas, though the Brazilian, if he is still around come September, will certainly see more pitch time than the Welshman.  It should be business as usual for all else.