Barca makes club history with win
Messi netted his league-leading eighth goal to open in the 21st minute, but he asked to be replaced eight minutes later after hurting a muscle in his right leg.
Adriano sealed the result in the 56th from a pass by Cesc Fabregas while Messi watched from the bench.
Messi's injury leaves him in doubt for Tuesday's Champions League match at Celtic.
While Barcelona may be missing Messi for the trip to Glasgow, it should have Neymar well rested after the striker didn't play a minute at Juegos Mediterraneos Stadium.
Barcelona's first-year coach Gerardo Martino has guided Barcelona to its best start in 82 leagues. Five other managers, including Pep Guardiola (2009-10) and predecessor Tito Vilanova (2012-13), had reached six wins.
''I have only latched on to one of the records that these players have broken and continue to break,'' said Martino. ''They have been doing so for years both individually and as a team. The fact that I formed a part of this one is circumstantial.''
Atletico Madrid could also establish a club milestone with a seventh win in as many games to begin the league when it visited Real Madrid late. Gareth Bale was up for his home debut for Madrid in the Spanish capital derby after missing the chance last weekend because of injury.
Elsewhere, Jonas scored his third winning goal for Valencia this week to secure a 1-0 victory at home over Rayo Vallecano.
The Brazilian forward netted the decisive goal in recent wins against Sevilla and Granada, and he stepped up once again to produce the 36th-minute winner after intercepting a poor pass by Rayo's Saul Niguez.
The promoted, and winless, Almeria did well to hold its own against the defending champions early on.
But after goalkeeper Esteban Suarez swatted Andres Iniesta's shot over the bar, it took Messi only a burst of speed and a quick one-two passing combination with Pedro Rodriguez to open up an angle and curl a left-footed shot off the post and into the net.
Messi's celebration was short-lived, however, when he asked to be substituted following an injury to his right thigh incurred during a long sprint to pressure Suarez. Messi has already missed one game this season with a left thigh bruise and several games at the end of last season due to a right hamstring pull.
The club said the Argentina forward would undergo more tests on Sunday.
Without Messi or Neymar, Barcelona struggled in attack and Almeria pushed the visitors into their area before the halftime whistle.
Barcelona regrouped during the break and Adriano redirected Fabregas' low cross home to complete a move started by Xavi Hernandez, who replaced Messi, and finish off any thoughts of an Almeria rally.
''I score when I can, but I try to defend well and then if I can provide something in attack, well that's great,'' said Adriano. ''Today I was able to score the goal that settled us down because the game was in a dangerous stage.''
Little-used Marc Bartra played well in Barcelona's defense with veterans Javier Mascherano and Carles Puyol injured.