ARLINGTON — Sitting behind sophomore Shane Buechele on the quarterbacking depth chart for Arlington Lamar, junior Andy Guinns opportunities were going to be slim this season.With Buechele sidelined by a foot injury, Guinn made the best of his first career start, leading the Vikings to a 44-36 upset win over Arlington Martin at Cravens Field on Friday night. Though Lamar (6-2, 4-1 in District 3-5A) led for the majority of the game, Guinn was forced to seal the victory on fourth-and-6 with just over a minute left and Lamars punter, also Buechele, unavailable. With the same demeanor he held from the first snap of the game, Guinn fired a quick pass to Andra Lemons-Hicks for 7 yards and a game-sealing first down.Before the play I just knew we had to do the right things, and I needed to make the right reads, Guinn said.Martin fell to 6-2 and 4-1.Guinn threw for 258 yards and a touchdown, completing 17 of 31 passes.Guinn said he knew he would get the nod Monday, but coach Trent Fuller said Guinns attitude throughout the season prepared him for Friday nights performance. Hes never once taken a day off because hes the backup or slacked on anything, Fuller said. Sometimes hes correcting me on my mistakes.Guinn wasnt the only Viking to have a team-carrying performance Friday.Senior running back Cameron Smith rushed for 161 yards and four touchdowns for the Vikings, and was key in converting several long third downs throughout the game.Guinns prime target was wide receiver Jaries King, standing 6-foot-4, He had nine catches for 187 yards and a touchdown.