The two-dimensional Hubbard model is studied within the composite operator method (COM) with the self-energy computed in the self-consistent Born approximation (SCBA). The COM describes interacting electrons in terms of the new elementary excitations that appear in the system owing to strong correlations; residual interactions among these excitations are treated within the SCBA. On decreasing the doping (from the overdoped to underdoped region), anomalous features develop in the spectral function $A(\mathbf{k},\ensuremath{\omega})$, the Fermi surface, the momentum distribution function $n(\mathbf{k})$, the dispersion, and the density of states $N(\ensuremath{\omega})$ in the intermediate-coupling regime $(U=8)$ at low temperatures $(T=0.01--0.02)$. At high doping $(n=0.7)$, the system resembles an ordinary weakly interacting metal. At low doping $(n=0.92)$, a pseudogap opens, hot and cold spots appear, and non-Fermi-liquid features develop. This behavior, together with the presence of kinks in the calculated electronic dispersion, is in agreement with angle-resolved photoemission spectroscopy data for high-${T}_{c}$ cuprates superconductors.