Fernando Mendoza will not start for the Las Vegas Raiders on Sunday, despite the team's four-game losing streak under veteran quarterback Kirk Cousins.

Head coach Klint Kubiak threw his support behind Cousins again on Monday, just hours after his team slipped to 3-4 following Sunday's loss to the Los Angeles Rams.

Mendoza was drafted No. 1 overall by Tom Brady's Raiders in this year's NFL Draft but has been forced to watch from the sideline for the majority of the season. 

The Raiders made a thrilling start to the NFL season, winning all of their opening three games, but the success has dried up and they have lost to the Rams, Buffalo Bills, New England Patriots and Kansas City Chiefs.

Kubiak has faced growing calls to give Mendoza, the reigning Heisman Trophy winner who led Indiana to the national championship last season, a chance this week against the woeful New York Jets.

But Kubiak backed Cousins, the 38-year-old former Minnesota Vikings and Atlanta Falcons quarterback, to return to form and announced he will keep the starting job for now.

'There is no controversy there,' Kubiak said. 'He's playing at a very high level.

'He's gotta continue to do that for us to win and we gotta keep helping all the areas around him. Excited for him to go play against the Jets.'

Kubiak did admit that Mendoza is 'going to play at some point,' but is reluctant to change while the Raiders are 'in the hunt' for a playoff spot.

Cousins was 26-of-44 for 295 yards and two touchdowns in Sunday's 35-21 loss to the Rams.

He has had an impressive start to the season and leads the NFL in touchdown passes with 16 and is third in passing yards with 1,877. 

Mendoza made his NFL debut against the Patriots in Week 5, completing six of eight passes for 48 yards.

'Kirk is playing really well, and we're in the hunt,' Kubiak continued. 'It's really important that we keep playing really well behind him and keep developing Fernando.

'Fernando is going to play at some point. It's not going to be this week.'