There's no stand out candidate for the 2nd opening slot so i thought i'd make a case for Kent captain and former England batsman Rob Key. Firstly, i'm not saying that he should be picked but i'd like to think he'd be considered, seeing as he is experienced, in good form and is a proper opener unlike other contenders Jonathan Trott, Ian Bell and Nick Compton.
Key is one of the most experienced players around and despite being 33, he is still scoring runs and, although he may not look it, is fit enough to continue for at least another few years. Key has previously played Test cricket - unlike all of the other contenders apart from Trott, Bell and Michael Carberry - and has a double century to his name. He's scored over 16,000 first class runs which is far more than any of the other openers around the county circuit. The Kent captain has 46 first class centuries which is 42 more than Joe Root and 20 more than Carberry.
Key is having a great season with the bat and in the County Championship, he's scored 729 runs at an average of over 45. It's not just his batting that could be useful for England, he's the longest serving county captain by a mile in recent times and could help guide the inexperienced Cook. Playing spin is what England struggle with and although Key is no spin maestro, he plays spin fairly well, using his feet and the sweep shot to good effect.
Apart from being 33, i can't see why he shouldn't be considered. He's a class batsman and his first class stats are second to none.