Sentence:  The most persistent tormentor was Alex Oxlade-Chamberlain, who scored a hat-trick in last month's corresponding fixture in Iceland. His ability to run at defences is <WSD>instantly</WSD> striking, but it is his clever use of possession that has persuaded some shrewd judges that he is an even better prospect than Theo Walcott. 
Meaning of the word marked with <WSD> tags:  At once; without delay. (from 16th c.)