Novak Djokovic enhanced his credentials as the greatest threat to Rafael Nadal winning a 12th French Open title next month after he beat Dominic Thiem on Saturday to reach the Madrid Open final. If Nadal overcomes the talented Stefanos Tsitsipas later on Saturday, it will be the Spaniard and Djokovic in Sunday’s final, in what could prove a dress rehearsal for the title match at Roland Garros too. World number one Djokovic’s 7-6 (7/2), 7-6 (7/4) win over Thiem was far from comfortable, the Madrid crowd treated to two exhilirating sets of baseline tennis, but the Serb found his best in both tie-breaks.In those pressure moments, Thiem, who saved two match points in beating Roger Federer in the quarter-finals, was unable to respond, even if he ran the top seed close enough to suggest he will be a serious contender again in Paris, where he was runner-up to Nadal last year.Since taking a month off after winning the Australian Open, Djokovic has stuttered, enduring early exits in Indian Wells, Miami and then Monte Carlo.But Thiem met the 31-year-old close to his best, delivering a timely reminder of why he has won the last three Grand Slam titles and will hold…