Losing 3 points in week 13 makes the points gap between Barcelona and Real Madrid increasingly narrow, meaning that Real Madrid has automatically reduced the points gap with Barcelona by 3 points now. Real Madrid has 1 match in hand and it could be used perfectly to reduce the points gap with Barcelona again. If in the end Real Madrid wins, then the gap between the two teams will only be 3 points, but I think Barcelona will improve in the next match, especially after the international break.
Right now the point difference between Real Madrid and Barcelona is six but remember Real Madrid has played one match less compared to Barcelona. So if Real Madrid is able to win the next match the point difference is going to be only three and that difference is going to be very easy for Real Madrid to overcome. Barcelona will have to be very careful. Nobody already expects them to win the Champions League title anyway. So they better do very well in the La Liga competition. They have a lot of young players in the squad. They can actually perform well with them. And I definitely do not want Barcelona to lose their credibility