I think the three veterans who really helped our side in recent years were Davids, Gallas, and Van der Vaart. Davids came in and we had our first two fifth place finishes of this era. He helped a lot with the maturation of our young midfielders like Carrick, Huddlestone, Lennon, and Jenas IMO.
Gallas and VDV came in during the same window and they were unparalleled in importance during our CL run. It is easy to forget just how good Gallas was in Champions League, he was imperious at times. He also got the Captain's band a few times very early in his tenure, shows how important he was. To have a guy who had played in a World Cup final and won the Premier League a couple of times was clearly great for us.
Then with Rafa he was unique because he was a veteran who still had a couple years left of his prime. We were so lucky to get a player like him and it's unlikely we'll find one again. He had the belief and understanding of a man who had played a significant amount at the top levels of football. That belief seeped into the rest of our attack and you could see the confidence he gave everyone else because he had the confidence in his own game which comes from experience. We have no player who has that confidence now. Eriksen flashes it occasionally but he's still a boy and isn't that same inspirational figure as Rafa.
Get some experienced geezers in to show the young lads how football is supposed to be played and how to behave like professionals and the wins will follow.