Ander Herrera has been a star player for Manchester United under Jose Mourinho, but the midfielder has explained the Red Devils' ability to "sign big players" will push him to work harder to impress his manager.
The Spain international moved to Old Trafford from Athletic Bilbao and has been in and out of the starting line-up when Louis van Gaal was in charge at the club. The former Real Madrid and Chelsea manager replaced the Dutchman and the 27-year-old has since been a regular inclusion in United's starting XI, making 37 starts across all competitions this season.
United spent a world-record fee of £89.3m ($112.3m) in re-signing Paul Pogba from Juventus last summer. Herrera, who revealed Mourinho's influence in becoming a key player for the Red Devils, said that he will keep working hard to improve his game.
"I am very thankful to him. This season has been the most regular one for me at the club and that is with Mourinho on the bench. I am very happy. He gave me, from the first day, a lot of confidence and he told me I was going to be an important player for him," Herrera told United's official website.
"I will always be thankful but football changes. We have great players and Manchester United has the capacity to sign big players, so I cannot sleep. I have to keep working, performing and giving what the manager wants me to give."
The former Bilbao midfielder's man of the match performance against Chelsea helped United seal a 2-0 victory over Premier League leaders at Old Trafford on 16 April. Herrera pointed out that fans would remember his performance only if the Red Devils finish the season on a high.
"I am happy with my development and I am happy with my performances, but people remember the end of the season and now we are in the crucial moment," he stressed.
"There are still eight Premier League games and hopefully four more Europa League games. Nobody will remember this part of the season if I don't perform well at the end. I am happy but I am not finished yet."
United are fifth on the Premier League table with 60 points after 31 games and trail fourth place Manchester City by four points. Mourinho's side have an advantage as they have a game in hand, while they are also fighting to win the Europa League.
The 20-time English champions settled for a 1-1 draw against Anderlecht in the first leg of the Europa League quarter-final tie in Belgium. The return leg will be played at Old Trafford on 20 April and a victory for United will see them make it to the last four of the Europe's second tier club competition.