United head into Sunday's clash with West Ham at Old Trafford having won only one of their previous six Premier League fixtures, a 3-1 triumph at Swansea.
In the other matches, they have been held at home 1-1 by Stoke, 0-0 by Burnley and 1-1 by Arsenal, drawn 0-0 at Liverpool and been thrashed 4-0 at Chelsea.
After the Red Devils on Thursday saw off Feyenoord 4-0 in the Europa League, United boss Jose Mourinho emphasised the need for his side - who he had recently described as "the unlucky team in the Premier League" - to convert their chances in domestic action.
Midfielder Herrera feels United are doing a good job in terms of fashioning scoring opportunities, but also has no doubt they need to be more clinical with them.
Herrera told United Review: "In football I think the most difficult thing is to create chances
To be in the third part of the pitch and getting good shots away and we are doing that.
"So the most difficult thing is what we are doing, but now we have to score the chances, that's what football is about
So of course we have to finish better."
Something else Mourinho spoke about after the Feyenoord game was the importance of players having an impact when selected, with his words indicating he felt forward Anthony Martial, who was left out of the matchday squad, had not done so of late.
The same cannot be said of Herrera, who has emerged as a key man in Mourinho's side.
The Spaniard only started one of United's opening five league games this term, but he has been in the first XI for all but one of the seven that have followed, being ruled out on that single occasion by suspension.
While understandably pleased with how things are going for him individually, Herrera - who also recently won his first Spain cap - knows he must keep producing the goods to justify his place.
"I am playing sometimes a little bit more defensive and sometimes also a bit further forward," said the 27-year-old, who was rested on Thursday, left as an unused substitute, and is expected to be back in the starting line-up on Sunday.
"I think it's good for me to be able to give some different options for the manager and the team.
"I am happy with my development but football has no memory so you have to perform every weekend and in every game."
Source: PA