It's a unanimous opinion that this is a juvenile Least Sandpiper. Many thanks to Alvaro, Joachim, Fred, Joe, and Dominik for commenting on it.
Though I accept the fact that I should concentrate more on the structure of this sandpiper that will help me to identify it correctly, I am still bothered by its plumage.
It's just late July now so shouldn't a juvenile Least Sandpiper (which should be among the earliest arrivals) possess a much brighter plumage than the bird I photographed? I compared all juvenile Least Sandpiper photos I took for the past 10 years and also browsed through images of juvenile Least Sandpiper in eBird Macaulay Library (using the filter juvenile/immature during July and August for all years) and notice they all have much brighter overall color with wider tawny edges and darker-centered feathers on lesser and median coverts.
The sandpiper that I photographed has grayish lesser and median coverts and almost no dark on the center of feathers.
Then I used the same filters (juvenile/immature during July) to search for Western Sandpiper in Macaulay Library and found these: https://ebird.org/media/catalog?bmo=7&taxonCode=wessan&mr=MCUSTOM&emo=7&q=Western%20Sandpiper%20-%20Calidris%20mauri&age=j
Much better match of the plumage with the sandpiper I photographed in my opinion and structure-wise is also quite similar.
I have even thought about the possibility of hybridization but couldn't find any documentation online about Least/Western or Least/Semipalmated Sandpiper Hybrid. By the way, Google 'calidris hybrid' and you will find some cool articles.
I will settle this bird as a juvenile Least Sandpiper as suggested for now and keep looking for the interesting ones to raise my, and hopefully yours too, curiosity.
Stay Safe and Happy Birding,