Siver skulle have ødt den tilbagevendende veteran [[B.J. Penn]] den 4. juni, 2016 på [[UFC 199]].<ref name="PennSiver">{{cite news|url=http://mmajunkie.com/2016/04/b-j-penn-vs-dennis-siver-slated-for-ufc-199-in-los-angeles|title=B.J. Penn vs. Dennis Siver slated for UFC 199 in Los Angeles|publisher=mmajunkie.com|author=Staff|date=2016-04-12|access-date=2016-04-12|archive-date=13. juli 2018|archive-url=https://web.archive.org/web/20180713044501/https://mmajunkie.com/2016/04/b-j-penn-vs-dennis-siver-slated-for-ufc-199-in-los-angeles|url-status=live}}</ref> Men Siver måtte melde afbud i starten af maj på grund af en ukendt skade.<ref>{{cite web|url=http://www.mmamania.com/2016/5/11/11645200/dennis-siver-injured-bounced-ufc-199-fight-against-bj-penn-los-angeles-mma|title=Dennis Siver injured, bounced from UFC 199 fight against BJ Penn|publisher=mmamania.com|author=Jesse Holland|date=2016-05-11|access-date=2016-05-11|archive-date=13. juli 2018|archive-url=https://web.archive.org/web/20180713042746/https://www.mmamania.com/2016/5/11/11645200/dennis-siver-injured-bounced-ufc-199-fight-against-bj-penn-los-angeles-mma|url-status=live}}</ref> Kampen mod Penn blev udskudt og fandt endelig sted den 25. juni, 2017 på [[UFC Fight Night: Chiesa vs. Lee]].<ref>{{cite news|url=http://mmajunkie.com/2017/03/b-j-penn-dennis-siver-johny-hendricks-tim-boetsch-at-ufc-fight-night-112-in-oklahoma-city|title=B.J. Penn-Dennis Siver, Johny Hendricks-Tim Boetsch at UFC Fight Night 112 in Oklahoma City|publisher=mmajunkie.com|author=Staff|date=2017-03-22|access-date=2017-03-22|archive-date=30. juni 2018|archive-url=https://web.archive.org/web/20180630161633/https://mmajunkie.com/2017/03/b-j-penn-dennis-siver-johny-hendricks-tim-boetsch-at-ufc-fight-night-112-in-oklahoma-city|url-status=live}}</ref> Siver vandt kampen via en tæt dommerafgørelse.<ref>{{Cite news|url=http://www.bjpenn.com/mma-news/ufc-fight-night-112/ufc-fight-night-112-results-dennis-siver-defeats-bj-penn-decision/|title=UFC Fight Night 112 results: Dennis Siver defeats BJ Penn by decision (highlights) {{!}} BJPenn.com|date=2017-06-25|work={{!}} BJPenn.com|access-date=2017-06-26|language=en-US|archive-date=11. juli 2018|archive-url=https://web.archive.org/web/20180711021822/https://www.bjpenn.com/mma-news/ufc-fight-night-112/ufc-fight-night-112-results-dennis-siver-defeats-bj-penn-decision/|url-status=live}}</ref>
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