Jose Reina
there's so much talk that he might leave after this season. and it's a shame because he's been such an immense player for us on numerous occasions and he's such an expert with penalties. even though he failed to stop them, he was able to guess the correct direction of the incoming ball. i've never seen him dive the other way. while players further up the field may grab more of the headlines, it is impossible to overstate the importance of a reliable goalkeeper.
Possible Replacements
Igor Akinfeev - made his debut at the tender age of 17 and has been a regular at CSKA ever since with 136 appearances to date.
Guillermo Ochoa - 47 caps for Mexico and widely regarded as one of the best young goalkeepers in the world.
Fernando Muslera - he kept clean sheets in all of Uruguay’s group matches and sent his nation through to the semi-finals of the competition by saving two penalties against Ghana. he made a total of 32 saves throughout the World Cup, the most of any goalkeeper.
David De Gea - 4th choice keeper for the Spainish team and considering the quality of the other 3 ahead of him, i'm sure he's pretty damn good. plus he is merely 19 i believe. currently on Manure's radar but would be nice to beat them to it.
Manuel Neur - i honestly think he has better distribution then Reina.
Diego Benaglio - Benaglio has been the Swiss first choice keeper since 2008 and helped Wolfsburg to gain the first Bundesliga in their history last season. and since his club is currently having a very hard time, we may be able to get him for a decent price.
Notable mentions: Ben Foster, Hugo Lloris and Piet Velthuizen.
Jamie Carragher
he's nowhere as fast as he was, and in time, he should no longer be an automatic starter. i for one, would be disappointed to see him start every game next season. without Carragher, we could possibly see the end of the hoof-ball tactics. so, while acknowledging Carragher as an amazing player who has stopped numerous scoring opportunities from the opponents and one who bleeds for the club, his clock is ticking very quickly.
Possible Replacements
Kyriakos Papadopoulus - we've been linked to him before. i don't know much about him but he's really highly rated. just 19 if i'm not mistaken.
Mamadou Sakho - this guy is a beast! would really love to have him in our team to give the much needed aggression we've been lacking.
Gary Cahill - has been in a series of commanding performances which has him stealing all the spotlight. Bolton aren't doing well financially so he could be a steal.
Micah Richards - he can play at rightback and also central defense. but with him being a City player, plus he is English, his price would probably be double his worth.
Simon Kjaer - another player from Wolfsburg.
Notable mentions: Per Mertesacker, Ryan Shawcross and Fabiano Santacroce.
Steven Gerrard
unlike the other 2 above, Gerrard is the hardest to replace IMO. i cannot think of any player whose combative style of play can lead a fightback.
Possible Replacements
Charlie Adam - he is actually being considered for the Player of the Season award. when was the last time a player from Blackpool was considered for an award which is usually won by players from the top 6 clubs?
Marek Hamsik - my personal first choice as he has all the attributes needed to be the next big thing.
Xabi Alonso - this is a long shot but well, i'm running out of options

Javi Martinez - already made over 100 appearances for the club both at home and abroad at the age of 21. tipped to be the perfect replacement for Alonso when he left us.
Notable mentions: Javier Pastore and Erik Lamela.