Djokovic showed great sportsmanship in the match when rain fell down heavily on Galan's side of the court as the new Court Philippe-Chatrier roof was closing, the Colombian slipped over. Djokovic responded by calling a pause of the match until the conditions came back equal for both sides.
Barca issued a communique shortly after the final whistle confirming Alba had "problems in his right hamstring," adding that he would undergo tests on Monday to discover the full extent of the injury.
"We are in a very strange situation, after a lot of months without much tennis, especially for me, that I didn't play in America, I don't know if it's a positive thing or a negative thing," Nadal said when asked how important it was to keep the early-round matches short and sweet.
Dongguan opened the first quarter on an 11-2 run, sparked by five straight points from Yang Shuyu.
"It was a very even match, perhaps more difficult than the result showed," said Djokovic, who is seeking for an 18th Grand Slam title.
Earlier in the women's race, the world record holder Brigid Kosgei defended her title in 2:18:58.
As expected, head coach Gustavo Alfaro included Fenerbahce forward Enner Valencia and teenage Sporting Lisbon winger Gonzalo Plata in his 30-man squad.
He has also maintained Wolverhampton forward, Adama Traore in his squad, despite the striker, who was born close to Barcelona, also being called up by his parents' homeland, Mali.
Both Li and Hao once played for Luneng, and worked for the club in the coaching team. Their replacement was viewed as a good sign for a smooth transition ahead of the rest of the CSL season. Enditem
The Red Bulls fired American coach Chris Armas last month and South African Bradley Carnell took over as interim coach.
PSV beat Fortuna Sittard 2-0 in Eindhoven on Sunday and passed Ajax on the Eredivisie table. Donyell Malen opened the scoring on a pass from Eran Zahavi in the fifth minute. In the remainder of the first half, four PSV goals were disallowed by the VAR for different reasons, meaning the match remained tight until the final minutes. Noni Madueke sealed the result four minutes from time.