The word enigma has been used to describe many a player over the years. Javier Luis Garcia, the amazingly talented ex-Liverpool winger, could conjure a goal out of thin air one game and seemingly be sitting in the crowd in the next game.
The great Paul Gasgoine was exceptionally prone to hot and cold games. He was not always able to show his exceptional footballing talent on a weekly basis.
When we look back on our memories of Gasgoine's career, how many of those memories are positive ones?
But the current enigma splitting opinions in the footballing community is Jermaine Pennant!
The current Reds winger is fighting to be part of the plans of Liverpool manager Rafael Benitez, doing himself no harm with his man of the match display in the game against Fulham on Saturday.
Pennant scored one goal and set up the other. But to date, his performance against the Cottagers has been Pennant's best display in a red shirt to date.
Pennant's strengths are his crossing ability and that he gives the Reds the necessary width to stretch teams across the pitch. He is also the only out and out winger plying his trade in the first team at Anfield.
But despite this, Benitez is more prepared to play Dirk Kuyt, Steven Gerrard or Yossi Benayoun out of position there.
The whole hot-and-cold theory is backed up when you consider Pennant's three first team goals that he's scored.
First, he scored a brilliant volley against Chelsea which won Liverpool the game.
His second was a fluke against Newcastle this season when a Toon Army defender cleared the ball only for it to hit Pennant and fly over the despairing Steve Harper for a goal.
His goal against Fulham yesterday was a true striker's finish. He beat two defenders for pace and smashed the ball home at the near post.
Liverpool, despite the boardroom rumblings, will once again be investing heavily in the transfer market. A goal-scoring right winger and a decent left back are the main targets.
Pennant's name has already been featured heavily in the gossip rumours linking him with serial under-achievers Newcastle and Tottenham. They will both try to break into the top four next season and challenge for silverware and European places.
When Pennant was signed from Birmingham for close to seven million, the transfer was received with mixed pleasing from both fans and staff on either side.
Steve Bruce, the selling manager, set Pennant's price tag at seven million thinking that he had as good as got the player's services again for next season in the Championship, not thinking that anyone in their right mind would pay that much for him.
While people associated with Liverpool couldn't quite see why the club hadn't just gone back in for Simao, the goalscoring Portuguese, then Benfica captain (now Athletico Madrid) who they had come so close to signing on two previous occasions.
Questions were also raised as to whether Pennant could hold his own at a top four club after his uneventful spell at Arsenal.
He scored a hat trick against Southampton, but he also got arrested and was continually sent out on loan to Watford, Leeds and Birmingham (Leeds and Birmingham were both relegated from the Premiership during his separate stays there).
The biggest game of his career was last year's Champions League Final against AC Milan, where Pennant was continuously given space down the right, but time after time his final ball was disappointing.
With Liverpool being mooted with the possible signing of either Blackburn's David Bentley or Porto's Ricardo Quaresma, time may be running out for Pennant's Reds career.