I really can't be bothered with this 'cos it's dragging this thread off-topic, but using Iniesta as an example in a European match against a lethargic, toothless United side to Modoric playing 38 games in the hustle and bustle of the Prem is a bit silly.
Despite his technical quality, Modoric has never been that dominant during his time at Spurs, and you only have to look at Luis Garcia who was twice the player in Europe as in the Prem to see that it does make a huge difference. The two Spurs fans I know, who're identical twins admittedly, think they overspent on a quality footballer who is, at best, inconsistent and they don't think he'll ever flourish in the Premiership. Having seen him 6 or 7 times this season I wouldn't disagree with them.
Size isn't everything; Scholes, Zola, etc are perhaps more fitting examples, but they were also blessed with an infinite amount of other footballing qualities, which more than compensated. The bottom line is, I don't think Modoric has enough of everything else. At best he'll be a good player for them. Not the great, mega effective £16M pound player he could be somewhere else.