Messi, enjoying another stunning season in front of goal, played no part in Argentina's friendly wins against El Salvador and Ecuador during the international break.
The 27-year-old superstar's availability was placed in doubt when Argentina boss Gerardo Martino - formerly of Barcelona - and international team-mate Sergio Aguero stated he was complaining of discomfort when putting his football boots on.
However, Messi took part in light training on Thursday before joining the rest of Barca's squad for a full session on Friday - boosting the chances of La Liga's all-time scorer playing at the Estadio de Balaidos.
Should Messi not make it, the likes of Neymar and Luis Suarez will be required to pick up the slack against a Celta side who bounced back from back-to-back defeats with victory at Levante before the international break.
Barcelona's 2-1 El Clasico victory over Real Madrid last time out moved them four points clear of their rivals at the top of the division.
That crucial win has given them breathing space but they would be foolish to take Celta lightly.
Celta, who sit 10th, beat Atletico Madrid in February, a result that significantly dented the reigning champions' hopes of retaining their title.
Barca coach Luis Enrique joined the club he represented with such distinction as a player from Celta in the close-season, replacing Martino.
And he will be more than aware of his former side's many threats on a weekend that will see Barca keen to avoid a slip-up, with Real expected to pick up all three points at home to second-bottom Granada.
Indeed, Celta claimed a stunning 1-0 win at Camp Nou earlier this season.
Joaquin Larrivey's goal settled November's clash, meaning that the Catalan giants will be out for revenge.
And they have won three out of their last four trips to Celta, including a 3-0 success last season that saw Alexis Sanchez and Cesc Fabregas - both no longer with the club - score.
Barca have also triumphed in five successive Liga away matches, scoring 20 goals in the process.
