I agree with you that Barcelona cannot catch up with Real Madrid at the top of the La Liga table. Real Madrid is leading Barcelona with 8 points, and it will be hard to drop points that will make Barcelona equal or overtake them at the top of the La Liga table.
Real Madrid and Barcelona, who seems promising for the title this season? Ofcourse you already know the answer, is Real Madrid. They have the best competitive squad this season and weighing up the balance for triumphant victory shouldn't be a problem for them. However, Barcelona are also retracing their steps and gradually falling back to becoming competitive again, if they're able to maintain consistency in their games, there's origination of challenge for Real Madrid who's also finding slight difficulties in winning matches.