Let the speed of the football player be, $v$.

Then, we can write

${\overrightarrow{v}}_i=v\left(-\hat{\mathrm{j}}\right)$ and ${\overrightarrow{v}}_f=v\left(\hat{\mathrm{i}}\right)$.

We can write force as, 

$$\begin{gathered} \overrightarrow{F}=m\overrightarrow{a} \\ =m\frac{{\overrightarrow{v}}_f-{\overrightarrow{v}}_i}{t} \\ =\frac{mv}{t}\left(\hat{\mathrm{i}}+\hat{\mathrm{j}}\right) \end{gathered}$$

Clearly, the direction of the force acting will be towards north-east.