UFC middleweight Kelvin Gastelum is reportedly being considered as the late replacement against Robert Whittaker for the April 17 Fight Night card, per Ariel Helwani.While replying to a now-deleted fan's tweet, Helwani tweeted that Gastelum's name is being discussed after Whittaker's original opponent Paulo Costa pulled out due to illness."I’m told that is at the very least being discussed. The one that got away? Let’s see," Ariel Helwani tweeted.I’m told that is at the very least being discussed. The one that got away? Let’s see. https://t.co/phz3oR9NSo— Ariel Helwani (@arielhelwani) March 16, 2021Former UFC middleweight champion and No. 1-ranked fighter Robert Whittaker (22-5 MMA, 13-3 UFC) was scheduled to fight No. 2-ranked Paulo Costa (13-1 MMA, 5-2 UFC) in the main event of UFC Fight Night 188 on April 17, 2021.Both Whittaker and Costa have lost to reigning champion Israel Adesanya in the past. The winner of the fight was likely to get a second crack at the title, especially if Whittaker won.Paulo Costa pulled out of the fight on March 17, and his team showed interest in rebooking the fight at a later date. However, the UFC has not announced whether the matchup will be kept intact.Paulo Costa is out of the April 17 main event versus Robert Whittaker, per multiple sources. He has the flu, not Covid, sources say. Team Costa is hoping the fight gets moved to May 1 or 8, but no word yet on what UFC will do.First reported by the BB, @guicruzzz.— Ariel Helwani (@arielhelwani) March 16, 2021Kelvin Gastelum [16-6 (1) MMA, 11-6 (1) UFC] tweeted a cryptic video following the bout's cancellation. He suggested that he was willing to step in against Robert Whittaker, who does not have an opponent as of now.#OnAmission4Gold pic.twitter.com/WJ6xheM2nY— #OnAmission4Gold (@KelvinGastelum) March 16, 2021Robert Whittaker vs. Kelvin Gastelum - The title fight that didn't materializeRobert Whittaker was scheduled to attempt a second successful middleweight title defense against Kelvin Gastelum at UFC 234 in February 2019. However, he was forced out of the fight hours earlier due to severe health complications.The pair went on to lose against Israel Adesanya in their next fights, and the subsequent career trajectories did not allow their paths to cross until this point. View this post on Instagram A post shared by Robert Whittaker (@robwhittakermma)The fight between Robert Whittaker and Kelvin Gastelum makes perfect sense at this point as both fighters are coming off convincing wins in their last fights.Whittaker extended his winning streak to two after losing the title to Adesanya with a win over Jared Cannonier at UFC 254. Gastelum scored his first win inside the UFC Octagon since May 2018 by defeating Ian Heinisch at UFC 258 in February 2021. View this post on Instagram A post shared by Kelvin Gastelum (@kgastelum)Robert Whittaker's recent wins over formidable opposition and Kelvin Gastelum's close fight with Israel Adesanya at UFC 236 are compelling points to stake a claim to the title with an impressive win if indeed the fight materializes.