The Argentina forward took his tally to an incredible 335 goals for the Catalan giants when he found the back of the net in a 1-1 draw at Real Sociedad on Wednesday.
Messi was not only able to celebrate Barca's progress into the Copa del Rey final - where they will face Real Madrid - but he also moved level with the record set by Athletic Bilbao's Telmo Zarra for the most goals scored for a single Spanish club.
The mercurial 26-year-old will fancy his chances of adding to his haul net against Vallecano, as he scored four times against the Madrid outfit last season and has struck on seven occasions in the last five meetings between the two sides.
Rayo have been taught some harsh lessons by Barcelona in recent years and will be up against in at Camp Nou this weekend.
Pedro scored a hat-trick as they were hammered 4-0 at home by the La Liga champions back in September and Paco Jemez's side have lost their last six games against the Catalan giants.
Barca have scored 26 goals in those encounters, with Vallecano having registered only one in response.
Rayo are second-bottom of the table, but will be buoyed by a 4-1 thrashing of Malaga last weekend.
That much-needed victory ended a run of three games without a win and raised hopes that they are capable of climbing the table.
Barca returned to the top of the table last Sunday with a 4-1 win of their own at Sevilla, and remarkably all three leading sides - Barca, Real Madrid, and Atletico Madrid - share the same win, draw, loss record.
Gerardo Martino's men suffered a 3-2 defeat against Valencia in their last home game in La Liga, but it would be a major shock if they are unable to beat Jemez's side.
Barca are set to welcome back Carles Puyol after the defender missed the last two games with a back problem.
Javier Mascherano and Jordi Alba played in the midweek cup victory and the duo are available to return to La Liga duty on Saturday after missing the win at Sevilla due to suspension.
Neymar (ankle) is closing in on a return, but Saturday's game will come too soon for the Brazil forward. Jonathan dos Santos (knee) is a long-term absentee and Oier Olazabal (finger) is also sidelined.
Romania full-back Razvan Rat could make his Vallecano debut after signing as a free agent on Thursday having been released by Premier League side West Ham last month.
Jemez has a doubt over Jonathan Viera, while Borja Lopez, Jose Carlos and Seba Fernandez will play no part.
