Pachuca won the opening leg on Thursday 3-2 at the Estadio Leon thanks to a brilliant performance from midfielder Dieter Villalpando and a brace from winger Enner Valencia.
The victory puts Pachuca in the box seat to win the Clausura championship.
Since the Liga MX finals series was introduced in the 2008-09 season, no team has lost the opening leg of the final at home and then gone on to be crowned champions.
Leon will be looking to end that trend on Sunday when they travel the 400 kilometres south-east to Pachuca for the second leg of the decider.
Gustavo Matosas' Leon side won the Apertura title when they smashed America 5-1 on aggregate, including a 3-1 away win.
The same result would see Leon triumph on Sunday as well.
Argentine striker Mauro Boselli will be critical to Leon's chances with the 28-year-old having notched 20 goals this season, although he has not hit the back of the net in three games.
Carlos Pena is Leon's second-most dangerous marksman this season with 12 goals and the midfielder scored the opening goal in the first leg against Pachuca on Thursday.
In a boost for Leon, Pachuca's home form over the past month has not been great with Enrique Meza's men having lost twice, drawn once and won once at the Estadio Miguel Hidalgo since the beginning of April.
Meza will undoubtedly turn to Valencia again for goals with the Ecuadorian winger having scored 18 this season, including two in the first leg, while Villalpando will pull the strings for Pachuca, after the 22-year-old midfielder set up all three of his team's goals on Thursday.
Pachuca are aiming for their first title since they took out the 2007 Clausura championship.
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