He can but he probably won't. He had the best season of his career last year and we still finished 5th and missed out on Champions League. He didn't make any more difference than Özil did when he was playing out of his skin the season before; we ended up 3rd that season with a bit of final day luck, and our campaign was still very disappointing on the whole.
People expect great players to lift the team a full level, and it's rarely ever the case unless they already have teammates who can match that level. Their top-end qualities are wasted otherwise. History is littered with great players who never accomplished much at bogstandard clubs. Totti recently ended his career with a single Serie A title and a couple Coppa Italia in 24 seasons. Roma have been in Champions League about as often as Spurs in the last 10-15 years despite having one of the greatest players of any generation.
The point I'm making is: don't sell either of them. Sign more players on their level instead. Everything else is a spectacular waste of time and effort.