  We give sufficient conditions on a Banach space $X$ which ensure that
$\ell_{\infty}$ embeds in $\mathcal{L}(X)$, the space of all operators on $X$.
We say that a basic sequence $(e_n)$ is quasisubsymmetric if for any two
increasing sequences $(k_n)$ and $(\ell_n)$ of positive integers with $k_n \leq
\ell_n$ for all $n$, we have that $(e_{k_n})$ dominates $(e_{\ell_n})$. We
prove that if a Banach space $X$ has a seminormalized quasisubsymmetric basis
then $\ell_{\infty}$ embeds in $\mathcal{L}(X)$.
