De Jong opened the scoring just before half-time with a tap-in on the line and then brilliantly set up substitute Riqui Puig to head home the second in the 89th minute.
Barca's away form has been terrible at times so the fact they've managed a run of seven straight matches away from Camp Nou with just one defeat -- against Athletic Bilbao in the Spanish Supercopa final, after extra-time -- is encouraging. The win at Elche was their fourth in a row on the road in La Liga, and even came without Messi.
On an individual note, De Jong continues to grow, Samuel Umtiti came in and did well and there was a nice moment for young midfielder Puig at the end as he scored his first goal for the club.
Sergio Busquets was booked for the fifth time this season and will be suspended for next week's home game against Barca's Supercopa conquerors, Athletic Bilbao.
Manager rating out of 10
6 -- Koeman was missing so many players that the team picked itself. Deserved credit for sticking Umtiti in. If he can help the Frenchman back to his best, it will be one of the most notable things he's done since taking over at Camp Nou.
Player ratings (1-10; 10 = best. Players introduced after 70 minutes get no rating)
DF Oscar Mingueza, 5 -- Wasteful with his deliveries in the final third and was grateful to Ter Stegen for stopping from Rigoni after he lost the ball in a dangerous position.
DF Ronald Araujo, 7 -- Continued his impressive form, giving very little away at the back. Was also more adventurous with his passing.
DF Samuel Umtiti, 7 -- A second start of the season and a second clean sheet. He's Barca's best defender on the ball, the doubt is whether he can stay fit and rediscover his pre-World Cup 2018 form.
DF Jordi Alba, 6 -- Up and down the left flank, contributing to the clean sheet in defence and also getting into good positions in attack.
MF Sergio Busquets, 6 -- Has found some form since Barca returned to a 4-3-3 formation and was once again impeccably positioned.
MF Frenkie de Jong, 8 -- Perhaps Barca's best player since the turn of the year. Scored his fourth goal of the season against Elche -- they have all come in his last 10 appearances -- and his driving run and cross for the Puig goal showed what he's capable of when getting forward more.
MF Pedri, 6 -- Neat and tidy on the ball but shot-shy in and around the area when chances came his way.
FW Ousmane Dembele, 6 -- Produced some moments of brilliance, gliding past two or three Elche players at a time, but often erred with his final decision.
FW Antoine Griezmann, 6 -- Not overly involved in the final third but worked hard. Koeman will want more from him.
FW Martin Braithwaite, 6 -- Produced a good cross for the opening goal from his starting position on the left wing and worked the line well in the second half.
MF Riqui Puig, NR -- Brought on for the final few minutes but found time to pop up at the far post to score his first-ever goal for the club.