What's the chances of getting into the position, what's then the chances of 1 goal determining the outcome of the game/tie and then what's the chances that De Gea will make a save that would win the game/tie that Lloris or similar wouldn't?
What you're suggesting is so unlikely to happen that, imo, you can't justify paying an additional £40m (once you factor in the bigger transfer fee, higher wages over 4-5 years and all other fees involved).
1stly you dont know how much it will be "extra" - I dont know how long Lloris has left at Spurs, but Utd will be lucky to get £25m for De Gea if he goes in the summer with one season remaining. Its also highly unlikely spurs will sell their no1 for anything like that unless his contract is running out in a similar amount of time.
Its also worth pointing out that its rare a team as big as Utd sell their No 1 player to a probable direct CL rival (look how much uproar happened about Di Maria even for £60m, Utd fans would rightly mutiny letting go of such a talent).
In your way, Utd would still end up paying the same amount to upgrade Lloris' contract (IF he ends up being good enough) in a few years time anyway so its not exactly going to make a big difference. Utd are also letting go of a player who they have put a lot of effort etc into backing to the hilt (not ignoriing his hard work also of course), and are only just starting to benefit from that.
Cant believe you would also say anything different if we were talking about a world class gk at Liverpool in the same situation
Yeah I don't think there's really a place in the team for Herrera unfortunately. Realistically the only position he could play is the one Carrick is occupying at the moment, and he's done a good job since coming back from injury.
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Herrera is SO not a DM its untrue. Playing a diamond (which is what Utd should do when the defence is sorted out), Herrera is a brilliant player ahead of the likes of Carrick /Blind/ Strootman? to go alongside Rooney or Di Maria and behind Mata / Rooney with two strikers ahead
Even as part of a 3 Herrera is a fantastic option to have depending on the team Utd are facing.
Herrera is a wonderful midfielder, really glad Utd got him (eventually), has an eye for goal (and from CM thats always a bonus) has a decent tackle but also the flair required. He has been frustrated with his rib injury and LvG chosing the wrong tactics / starting personnel for quite a few games in the last month or so, but he will be a mainstay in the squad for some time I hope.